UNDERWRITING AGREEMENT

(iii)          “Final Term Sheet” means the final term sheet in the form attached as Schedule III hereto and prepared and filed pursuant to Section 4(a) hereof;

(iv)          “Issuer Free Writing Prospectus” means each “free writing prospectus” (as defined in Rule 405 under the Act), including the Final Term Sheet, prepared by or on behalf of the Company or used or referred to by the Company in connection with the offering of the Debt Securities;

(v)           “Preliminary Prospectus” means any preliminary form of prospectus supplement relating to the Debt Securities (together with the base prospectus in the form in which it appears in the Registration Statement) which has heretofore been or is required to be filed by the Company pursuant to Rule 424 under the Act and is used prior to the filing of the Prospectus;

(vi)          “Pricing Disclosure Package” means, as of the Applicable Time, the most recent Preliminary Prospectus, together with each Issuer Free Writing Prospectus filed or used by the Company on or before the Applicable Time (including the Final Term Sheet);

(vii)         “Prospectus” means the base prospectus contained in the Registration Statement as supplemented by the final prospectus supplement relating to the Debt Securities, in the form in which such base prospectus as so supplemented shall be filed by the Company with the Commission pursuant to Rule 424 under the Act; and

(viii)        “Registration Statement” means, collectively, the various parts of such registration statement, each as amended as of the Effective Date for such part, including any Preliminary Prospectus or the Prospectus and all exhibits to such registration statement.

Any reference herein to the Registration Statement, the Preliminary Prospectus or the Prospectus shall be deemed to refer to and include the documents incorporated by reference therein pursuant to Item 12 of Form S-3 which were filed under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), on or before the date of this Agreement; and, if the Company files any document pursuant to the Exchange Act after the date of this Agreement and prior to the termination of the offering of the Debt Securities by the Underwriters, which documents are deemed to be incorporated by reference into the Prospectus, such filing shall constitute an amendment or supplement to the Prospectus.  Any reference to the “most recent Preliminary Prospectus” shall be deemed to refer to the latest Preliminary Prospectus included in the Registration Statement or filed pursuant to Rule 424(b) under the Act prior to or on the date hereof (including for purposes hereof, any documents incorporated by reference therein prior to or on the date hereof).  There are no contracts or documents of the Company that are required to be filed as exhibits to the Registration Statement or any documents incorporated by reference therein by the Act, the Exchange Act or the rules and regulations thereunder which have not been so filed.

(b)       No order preventing or suspending the use of any Preliminary Prospectus, the Prospectus or the Registration Statement has been issued by the Commission and no proceeding for that purpose has been initiated or threatened by the Commission.

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(c)       The Registration Statement, on the Effective Date, complied in all material respects with the requirements of the Act, the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”), and the respective rules and regulations of the Commission thereunder and did not contain any untrue statement of a material fact or omit any material fact required to be stated therein or necessary in order to make the statements therein not misleading; and, at the time the Prospectus is filed with the Commission and at the Closing Date (as hereinafter defined), the Prospectus will comply in all material respects with the Act and the rules and regulations of the Commission thereunder and will not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading;  provided that the Company makes no representations or warranties as to (A) that part of the Registration Statement which shall constitute the Statement of Eligibility (Form T-1) under the Trust Indenture Act of the Trustee, (B) the information contained in or omitted from the Registration Statement or the Prospectus in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of any Underwriter through the Representatives specifically for use in the Registration Statement or Prospectus, which information is specified in Section 10(g) hereof or (C) the statements set forth in the twelfth paragraph in the section entitled “Underwriting” furnished directly by Lazard Capital Markets LLC.  Each Preliminary Prospectus and the prospectus filed as part of the Registration Statement as originally filed or as part of any amendment thereto, or filed pursuant to Rule 424 of the Act, complied when so filed in all material respects with the rules under the Act, and each Preliminary Prospectus and the Prospectus delivered to the Underwriters for use in connection with this offering was identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(d)       The documents incorporated by reference in any Preliminary Prospectus or the Prospectus, when filed with the Commission, conformed, or will conform, in all material respects to the requirements of the Exchange Act and the rules and regulations of the Commission thereunder; and none of such documents included, or will include, any untrue statement of a material fact or omitted or will omit to state any material fact required to be stated therein or necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading.

(e)       The Pricing Disclosure Package, as of the Applicable Time did not, and as of the Closing Date will not, contain any untrue statement of a material fact or omit any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading; provided that the Company makes no representations or warranties as to (A) the information contained in or omitted from the Pricing Disclosure Package in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of any Underwriter through the Representatives specifically for use in the Pricing Disclosure Package, which information is specified in Section 10(g) hereof or (B) the statements set forth in the twelfth paragraph in the section entitled “Underwriting” furnished directly by Lazard Capital Markets LLC.

(f)        Prior to the execution of this Agreement, the Company has not made and will not make any offer relating to the Debt Securities that would constitute an Issuer Free Writing Prospectus (other than the Final Term Sheet) without the prior consent of the Representatives;

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the Company has complied and will comply with the requirements of Rule 433 under the Act with respect to any such Issuer Free Writing Prospectus; any such Issuer Free Writing Prospectus will not, as of its issue date and through the Closing Date, include any information that conflicts with the information contained in the Registration Statement and the Prospectus; and any such Issuer Free Writing Prospectus, when taken together with the information contained in the Registration Statement and the Prospectus, did not, when issued or filed pursuant to Rule 433, and does not contain any untrue statement of a material fact or omit any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading.

(g)       The Company is not, and after giving effect to the offering and sale of the Debt Securities and the application of the proceeds thereof as described in the Pricing Disclosure Package and Prospectus will not be, an “investment company” or an entity “controlled” by an “investment company” within the meaning of the Investment Company Act of 1940, as amended, without taking account of any exemption arising out of the number of holders of the Company’s securities.

(h)       The statements in the most recent Preliminary Prospectus and Prospectus under the headings “Supplemental Description of Debt Securities” and “Description of the Debt Securities” fairly summarize the matters therein described.

(i)        This Agreement has been duly authorized, executed and delivered by the Company.

(j)        The Indenture has been duly authorized by the Company and the Indenture (excluding the Supplemental Indenture) has been, and at the Closing Date the Indenture will have been, duly executed and delivered by the Company; and, assuming due authorization, execution and delivery by the Trustee, the Indenture (excluding the Supplemental Indenture) constitutes, and, at the Closing Date, the Indenture will constitute, a legal, valid and binding obligation of the Company, enforceable in accordance with its terms, except as enforcement thereof may be limited by laws and principles of equity affecting the enforcement of creditors’ rights, including, without limitation, bankruptcy and insolvency laws; and the Indenture has been duly qualified under the Trust Indenture Act.

(k)       The issuance and sale by the Company of the Debt Securities pursuant to this Agreement have been duly authorized by all necessary corporate action; and, when issued, authenticated and delivered to the Underwriters pursuant to this Agreement against payment of the consideration therefor specified herein, the Debt Securities will be valid and binding obligations of the Company, enforceable in accordance with their terms, except as enforcement thereof may be limited by laws or principles of equity affecting creditors’ rights, including, without limitation, bankruptcy and insolvency laws, and will be entitled to the benefits of the Indenture.

(l)        The issuance and sale of the Debt Securities have been duly authorized and approved by an order of The New Mexico Public Regulation Commission and such order is final and in full force and effect on the date hereof, the time for appeal therefrom or review thereof or intervention with respect thereto having expired; no further approval, authorization,

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consent or other order of any public board or body is legally required in connection with the transactions contemplated by this Agreement and the Indenture, except for the registration under the Act of the Debt Securities and as may be required under the blue sky laws of any jurisdiction in connection with the purchase and distribution of the Debt Securities by the Underwriters in the manner contemplated herein and in the Prospectus.

(m)      Neither the execution and delivery of this Agreement or the Supplemental Indenture, the issue and sale of the Debt Securities, nor the consummation of any other of the transactions herein or therein contemplated, nor the fulfillment of the terms hereof or thereof will conflict with, result in a breach or violation or imposition of any lien, charge or encumbrance upon, any property or assets of the Company, other than the liens and security interests created by the Indenture, pursuant to, (i) the charter or by-laws of the Company; (ii) the terms of any indenture, contract, lease, mortgage, deed of trust, note agreement, loan agreement or other agreement, obligation, condition, covenant or instrument to which the Company is a party or bound or to which its property is subject; or (iii) any statute, law, rule, regulation, judgment, order or decree applicable to the Company of any court, regulatory body, administrative agency, governmental body, arbitrator or other authority having jurisdiction over the Company or any of its properties except, in the case of clause (ii), any such conflict, default, breach or violation which would not, individually or in the aggregate, have a material adverse effect on the condition (financial or otherwise), prospects, earnings, business or properties of the Company, whether or not arising from transactions in the ordinary course of business.

(n)       The Company has good and valid title to all real and fixed property and leasehold rights and personal property which are owned by it, subject only to taxes and assessments not yet delinquent; as to parts of the Company’s property, certain easements, conditions, restrictions, leases, and similar encumbrances which do not affect the Company’s use of such property in the usual course of its business, certain minor defects in titles which are not material, defects in titles to certain properties which are not essential to the Company’s business and mechanics’ lien claims being contested or not of record or for the satisfaction or discharge of which adequate provision has been made by the Company; and any real property and buildings held under lease by the Company are held by it under valid, subsisting and enforceable leases with such exceptions as are not material and do not interfere with the use made and proposed to be made of such property and buildings by the Company.

(o)       The historical financial statements and schedules of the Company included or incorporated by reference in the Registration Statement, Pricing Disclosure Package and Prospectus present fairly in all material respects the financial condition, results of operations, cash flows and changes in financial position of the Company as of the dates and for the periods indicated, comply as to form with the applicable accounting requirements of the Act and the Exchange Act and have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) throughout the periods involved (except as otherwise noted therein) and comply, and at the Closing Date will comply, in all material respects with the requirements of paragraph (e) of Item 10 of Regulation S-K; the selected financial data set forth under the caption “Selected Financial Data” in the most recent Preliminary Prospectus and Prospectus fairly present, on the basis stated in the Pricing Disclosure Package and Prospectus, the information included therein. Except as disclosed in or incorporated by reference in the

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Registration Statement, Pricing Disclosure Package and Prospectus, there are no contingent obligations which are material to the Company.

(p)       Deloitte & Touche LLP, which audited the financial statements and the related financial statement schedule as of and for the year ended December 31, 2005 incorporated by reference in the Registration Statement, Pricing Disclosure Package and Prospectus from the Company’s Annual Report on Form 10-K for the year ended December 31, 2005, (i) is an independent registered public accounting firm as required by the Act and the rules and regulations of the Commission thereunder and (ii) is in compliance with its obligations under the Exchange Act with respect to the Company.

(q)       The statistical and market-related data and forward-looking statements (within the meaning of Section 27A of the Act and Section 21E of the Exchange Act) included or incorporated by reference in the Pricing Disclosure Package and Prospectus are based on or derived from sources that the Company believes to be reliable and accurate in all material respects and represent good faith estimates that are made on the basis of data derived from such sources.

(r)        Except as may otherwise be reflected in or contemplated by the Registration Statement, Pricing Disclosure Package and Prospectus, since the respective dates as of which information is given in the Registration Statement, Pricing Disclosure Package and Prospectus (i) there has been no material adverse change in the condition (financial or otherwise), prospects, earnings, business or properties of the Company, whether or not arising from transactions in the ordinary course of business and (ii) the Company has not entered into any transactions which are material to the Company, other than in the ordinary course of business; and, except as so reflected or contemplated, there are no contingent obligations which are material to the Company.

(s)       The Company has been duly incorporated and is validly existing as a corporation in good standing under the laws of the jurisdiction in which it is chartered or organized with full corporate power and authority to own or lease, as the case may be, and to operate its properties and conduct its business as described in the Registration Statement, Pricing Disclosure Package and Prospectus, and is duly qualified to do business as a foreign corporation and is in good standing under the laws of each jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except where the failure to be so qualified would not have a material adverse effect on the condition (financial or otherwise), prospects, earnings, business or properties of the Company, whether or not arising from transactions in the ordinary course of business.

(t)        The Company has no subsidiaries.

(u)       The Company is not in conflict, violation, breach or default of (i) any provision of its charter or bylaws; (ii) the terms of any indenture, contract, lease, mortgage, deed of trust, note agreement, loan agreement or other agreement, obligation, condition, covenant or instrument to which it is a party or bound or to which its property is subject; or (iii) any statute, law, rule, regulation, judgment, order or decree applicable to the Company of any court,

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regulatory body, administrative agency, governmental body, arbitrator or other authority having jurisdiction over the Company or any of its properties, as applicable, except, in the case of clause (ii) or (iii), any such conflict, violation, breach or default which would not, individually or in the aggregate, (x) have a material adverse effect on the condition (financial or otherwise), prospects, earnings, business or properties of the Company, whether or not arising from transactions in the ordinary course of business and (y) impair the validity of the Debt Securities.

(v)       Neither the Company, nor any director, officer, agent, employee or other person or entity acting on behalf of the Company has, in the course of its actions for, or on behalf of, the Company, used any corporate funds for any unlawful contribution, gift, entertainment or other unlawful expenses relating to political activity; made any direct or indirect unlawful payment to any foreign or domestic government official or employee from corporate funds; or made any unlawful bribe, rebate, payoff, influence payment, kickback or other unlawful payment to any foreign or domestic government official or employee.

(w)      (i) the Company has devised and established and maintains the following, among other, internal controls (without duplication): (A) a system of “internal accounting controls” as contemplated in Section 13(b)(2)(B) of the 1934 Act; (B) “disclosure controls and procedures” as such term is defined in Rule 13a-15(e) under the 1934 Act; and (C) “internal control over financing reporting” (as such term is defined in Rule 13a-15(f) under the 1934 Act (the internal controls referred to in clauses (A) and (B) above and this clause (C) being hereinafter called, collectively, the “Internal Controls”); (ii) the Internal Controls are evaluated by the Company’s senior management periodically as appropriate and, in any event, as required by law; and (iii) based on the most recent evaluations of the Internal Controls, (A) the Internal Controls are, individually and in the aggregate, effective in all material respects to perform the functions for which they were established; and (B) all material weaknesses, if any, and significant deficiencies, if any, in the design or operation of the Internal Controls which are reasonably likely to adversely affect the Company’s ability to record, process, summarize and report financial information and any fraud, whether or not material, that involves management or other employees who have a significant role in the Internal Controls have been disclosed to the Company’s independent auditors and the audit committee of the Company’s board directors.

(x)        Except as set forth in, or incorporated by reference in, the Registration Statement, Pricing Disclosure Package and Prospectus, the Company (i) is in compliance with any and all applicable federal, state and local laws and regulations relating to the protection of human health and safety, the environment or hazardous or toxic substances or wastes, pollutants or contaminants (“Environmental Laws”), (ii) has received all permits, licenses or other approvals required of them under applicable Environmental Laws to conduct their respective businesses, (iii) is in compliance with all terms and conditions of any such permits, licenses or approvals, and (iv) has not received notice of any actual or potential liability for the investigation or remediation of any disposal or release of hazardous or toxic substances or wastes, pollutants or contaminants, except where such non-compliance with Environmental Laws, failure to receive required permits, licenses or other approvals, or any such liability would not, individually or in the aggregate, have a material adverse effect on the condition (financial or otherwise), prospects, earnings, business or properties of the Company, whether or not arising from transactions in the ordinary course of business.

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(y)       With respect to each employee benefit plan (as defined in Section 3(3) of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”)) which the Company or any other organization that together with the Company is treated as a single employer under Sections 414(b), (c), (m) or (o) of the Internal Revenue Code of 1986, as amended (the “Code”) (an “ERISA Affiliate”), has at any time sponsored, maintained, contributed to or been obligated to contribute to (a “Plan”): (i) the Company and each ERISA Affiliate have administered and operated each Plan sponsored or maintained by the Company or an ERISA Affiliate in compliance with ERISA, the Code and other applicable laws except for such instances of noncompliance as have not resulted in and could not reasonably be expected to result in a material liability to the Company or ERISA Affiliate; (ii) each Plan sponsored or maintained by the Company or an ERISA Affiliate intended to qualify under Section 401(a) of the Code so qualifies and to the Company’s knowledge nothing has occurred, whether by action or failure to act, which could reasonably be expected to cause the loss of such qualification of any such Plan; (iii) neither the Company nor any ERISA Affiliate has incurred, and to the Company’s knowledge no event, transaction or condition has occurred or exists under which the Company or any ERISA Affiliate could reasonably expect to incur, any material liability or the imposition of any lien on any of the rights, properties or assets of the Company or any ERISA Affiliate pursuant to Title I or Title IV of ERISA (other than routine claims for benefits) or applicable penalty or excise provisions of the Code; (iv) there has been no reportable event (within the meaning of Section 4043 of ERISA) with respect to any Plan subject to Title IV of ERISA that is sponsored or maintained by the Company or an ERISA Affiliate for which the 30-day reporting requirement has not been waived which could reasonably be expected to result in a material liability under Title IV of ERISA to the Company or an ERISA Affiliate; (v) no accumulated funding deficiency (within the meaning of Section 302 of ERISA and Section 412 of the Code), whether or not waived, exists with respect to any Plan subject to Title IV of ERISA that is sponsored or maintained by the Company; and (vi) neither the Company nor any ERISA Affiliate has incurred, and to the Company’s knowledge no event, transaction or condition has occurred or exists under which the Company or any ERISA Affiliate could reasonably expect to incur, any material liability with respect to termination of, or withdrawal from, any Plan subject to Title IV of ERISA.

(z)        The franchises held by the Company, together with the applicable Certificates of Convenience and Necessity issued by The New Mexico Public Regulation Commission, the Public Utility Commission of Texas and the Kansas Corporation Commission, give the Company all necessary authority for the maintenance and operation of its properties and business as now conducted, and are free from burdensome restrictions or conditions of an unusual character.

(aa)     The Company is not an “ineligible issuer” as defined under the Act.

(bb)     The Company is in compliance in all material respects with the Sarbanes-Oxley Act of 2002 and the rules and regulations of the Commission thereunder, to the extent that such Act and such rules are in effect and applicable to the Company.

(cc)     The Company has complied and will comply with the requirements of Rule 433 under the Act applicable to any free-writing prospectus, including timely filing with the Commission and legending.

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(dd)     The Company has not taken, directly or indirectly, any action which is designed to or which has constituted or which might reasonably have been expected to cause or result in stabilization or manipulation of the price of any security of the Company in connection with the offering of the Debt Securities.

Any certificate signed by any officer of the Company and delivered to the Representatives or counsel for the Representatives in connection with the offering of the Debt Securities shall be deemed a representation and warranty by the Company, as to matters covered thereby, to each Underwriter.

2.              Purchase and Sale .   Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company agrees to sell to the Representatives and each other Underwriter, and the Representatives and each other Underwriter agree, severally and not jointly, to purchase from the Company, at the purchase prices set forth in Schedule I hereto, the respective principal amounts of the Debt Securities set forth opposite their respective names in Schedule II hereto.

3.              Delivery and Payment .  Delivery of and payment for the Debt Securities shall be made at the place, date and time specified in Schedule I hereto, which date and time may be postponed by agreement between the Representatives and the Company (such date and time being herein called the “Closing Date”).  Delivery of the Debt Securities shall be made to the Representatives for the respective accounts of the several Underwriters against payment by the several Underwriters through the Representatives of the purchase price thereof to or upon the order of the Company in federal (same day) funds.  The Debt Securities will be delivered in definitive registered form except that, if for any reason the Company is unable to deliver the Debt Securities in definitive form, the Company reserves the right, as provided in the Indenture, to make delivery in temporary form.  Any Debt Securities delivered in temporary form will be exchangeable without charge for Debt Securities in definitive form.  Unless otherwise indicated on Schedule I, the Debt Securities will be registered in the name of Cede & Co., as nominee of The Depository Trust Company and in the principal amounts set forth in Schedule II hereto.  The Debt Securities will be made available to the Representatives for checking in New York, New York, not later than 2:00 p.m., New York City time, on the business day preceding the Closing Date.

4.              Agreements of the Company .   The Company agrees with the several Underwriters that:

(a)       The Company will prepare the Final Term Sheet, containing solely a description of the terms of the Debt Securities and of the offering, in the form attached as Schedule III hereto, will file such Final Term Sheet pursuant to Rule 433(d) under the Act and will notify the Representatives promptly of such filing.  The Company will prepare the Prospectus, in a form approved by the Representatives, will file the Prospectus pursuant to Rule 424(b) under the Act and will notify the Representatives promptly of such filing.  During the period for which a prospectus relating to the Debt Securities is required to be delivered under the Act (whether physically or through compliance with Rule 172 under the Act or any similar rule), the Company will promptly advise the Representatives (i) when any amendment to the Registration Statement shall have become effective, (ii) when any subsequent amendment or

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supplement to the Prospectus (including documents deemed to be incorporated by reference into the Prospectus) has been filed, (iii) of any request by the Commission for any amendment of or supplement to the Registration Statement or the Prospectus or for any additional information and (iv) of the issuance by the Commission of any stop order or of any order preventing or suspending the use of the Prospectus or any Issuer Free Writing Prospectus, of the suspension of the qualification of the Debt Securities for offering or sale in any jurisdiction, of the initiation or threatening of any proceeding or examination for any such purpose, of any request by the Commission for the amending or supplementing of the Registration Statement, the Prospectus or any Issuer Free Writing Prospectus or for additional information.  During the period for which a prospectus relating to the Debt Securities is required to be delivered under the Act (whether physically or through compliance with Rule 172 under the Act or any similar rule), the Company will not file any amendment of the Registration Statement or supplement to the Prospectus (including documents deemed to be incorporated by reference into the Prospectus) unless the Company has furnished to the Representatives a copy for their review prior to filing and will not file any such proposed amendment or supplement to which the Representatives reasonably object.  In the event of the issuance of any stop order or of any order preventing or suspending the use of the Prospectus or any Issuer Free Writing Prospectus, the Company will promptly use its best efforts to obtain the withdrawal of such order.  In the event of the Company’s receipt of a notice objecting to the use of the form of the Registration Statement or any post-effective amendment thereto, the Company will promptly take such steps including, without limitation, amending the Registration Statement or filing a new registration statement, at its own expense, as may be necessary to permit offers and sales of the Debt Securities by the Underwriters (and references herein to the “Registration Statement” shall include any such amendment or new registration statement).

(b)       If, at any time when a prospectus relating to the Debt Securities is required to be delivered under the Act (whether physically or through compliance with Rule 172 under the Act or any similar rule), any event occurs as a result of which the Prospectus as then amended or supplemented would include any untrue statement of a material fact or omit to state any material fa