Document:

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                                                               Exhibit 10.12 (f)

                                   AMENDMENT

         THIS AMENDMENT, dated as of March 30, 1999 ("Amendment"), between
UNION PACIFIC RESOURCES GROUP INC., a Utah corporation (the "Company"), and
KERRY R. BRITTAIN (the "Executive") amends the Agreement between the Company
and Executive entered into on March 18, 1999 (the "Agreement"). Defined terms
used herein shall have the meanings as set forth in the Agreement unless
otherwise defined herein.

1.       The Agreement is hereby amended to add a new Section 5.4 to read in
         its entirety as follows:

         Notwithstanding any provision herein or any provision in the Company's
         1995 Stock Option and Retention Stock Plan (or any agreement entered
         into thereunder) to the contrary (except any contrary provision
         dealing with a pooling of interests transaction), (A) upon a Change in
         Control, any Option then held by the Executive (other than an Option
         the exercisability of which is based exclusively on the attainment of
         performance targets which, at the time of the Change in Control, have
         not been met), shall be fully exercisable and any restriction on any
         Retention Share then held by the Executive (other than a Retention
         Share the vesting of which is based exclusively on the attainment of
         performance targets, which, at the time of the Change in Control, have
         not been met) shall lapse or be deemed fully satisfied, as applicable,
         and (B) if, following a Change in Control and during the term of this
         Agreement, the Executive is terminated by the Company for any reason
         other than Cause or the Executive terminates with Good Reason, then,
         with respect to any Option then held by the Executive, the Executive
         (or his Beneficiary, if applicable) shall have the right to exercise
         such Option at any time during the earlier of (i) the five-year period
         following such termination or (ii) the term of the Option; provided,
         however, that, with respect to any provision in (A) or (B) in this
         Section 5.4, if it is intended that the transaction constituting a
         Change in Control be accounted for as a pooling of interests under
         Accounting Principles Board Opinion No. 16 (or any successor thereto),
         and if the existence and/or operation of any such provision would
         violate Paragraph 47(c) thereof (or any successor thereto), then any
         such provision shall (in whole or in part to the minimum extent
         necessary to avoid a violation) be deemed null and void ab initio
         and/or any operation of such provision shall (in whole or in part to
         the minimum extent necessary to avoid a violation) be deemed to have
         no force or effect under law; provided further, however, that the
         foregoing proviso shall apply only if the transaction is otherwise
         eligible to be accounted for as a pooling of interests.

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         Except as amended hereby, all other terms and provisions shall remain
in full force and effect

         IN WITNESS WHEREOF, all parties hereto have executed this Amendment as
of the date and year first above written.

                                           UNION PACIFIC RESOURCE GROUP INC.

                                           By:
                                               --------------------------------
                                                          JACK L. MESSMAN

                                           EXECUTIVE

                                           By:

                                                          KERRY R. BRITTAIN<PAGE>   1
                                                                EXHIBIT 10.16(c)

                                 ASSIGNMENT AND
                              CONSENT TO ASSIGNMENT

         THIS ASSIGNMENT AND CONSENT TO ASSIGNMENT ("Assignment") is made and
entered into this 1st day of March, 1999, by and among UNION PACIFIC FUELS, INC.
("UPFI"), UNION PACIFIC RESOURCES COMPANY ("UPRC") and KERN RIVER GAS
TRANSMISSION COMPANY ("Kern River").

                                    RECITALS:

         WHEREAS, Kern River and UPFI are parties to that certain Transportation
Agreement dated December 15, 1989 (Contract 1005), as amended, and that certain
Transportation Agreement dated December 7, 1990 (collectively, the
"Transportation Agreements"); and

         WHEREAS, UPFI desires to assign the Transportation Agreements to UPRC;

         NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained, Kern River, UPFI and UPRC do hereby agree as follows:

                                   AGREEMENT:

         1.       UPFI hereby assigns to UPRC all of UPFI's rights, interest and
                  obligations arising out of and to be received or performed
                  under the Transportation Agreements.

         2.       UPRC accepts such assignment of UPFI's rights, interests and
                  obligations under the Transportation Agreements. UPRC will
                  have the rights and obligations of the "Shipper" under the
                  Transportation Agreements and will be bound by the obligations
                  of UPFI under the Transportation Agreements to the same extent
                  as UPRC would be bound if UPRC, rather than UPFI, were the
                  signatory to the Agreements and identified as "Shipper" in the
                  recitals, and to the same extent as if UPRC's name appeared in
                  the Transportation Agreements in each place where appears the
                  name "UPFI." UPRC will receive any refunds or adjustments due
                  to UPFI with respect to Assignment, and UPRC will fulfill the
                  obligations of UPFI with respect to the Transportation
                  Agreements that arose prior to the effective date of this
                  Assignment, including the obligations to pay demand charges
                  applicable to such service.

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         3.       Kern River consents to the assignment of the Transportation
                  Agreements from UPFI to UPRC, and Kern River relieves UPFI of
                  any responsibilities or obligations arising under the
                  Transportation Agreements for services after March 31, 1999.

         4.       In accordance with Section 17.1 of the Transportation
                  Agreements, this Assignment shall become effective on April 1,
                  1999; provided, however, UPRC may itself, or through an agent,
                  nominate under the Transportation Agreements on March 31,
                  1999, for the gas day April 1, 1999.

         5.       This Assignment shall be binding upon and inure to the benefit
                  of the parties hereto and any successors or assigns of such
                  parties.

         6.       This Assignment may be executed in any number of counterparts.

         IN WITNESS WHEREOF, Kern River, UPFI and UPRC have caused this
Assignment to be duly executed as of the date first written above

                           KERN RIVER GAS TRANSMISSION
                              COMPANY

                            By:
                                ------------------------------------------------
                            Name:  Larry E. Larsen
                            Title: Vice President-Customer Services and Rates

                            UNION PACIFIC FUELS, INC.

                            By:
                                ------------------------------------------------
                            Name:  Troy M. Smith
                            Title: Manager, Transportation

                            UNION PACIFIC RESOURCES COMPANY

                            By:
                                ------------------------------------------------
                            Name:  Robert E. Lindsey
                            Title: Attorney-In-Fact<PAGE>   1

                                                               EXHIBIT 10.22 (f)

                                 AMENDMENT NO. 5
                                       TO
                          MERGER AND PURCHASE AGREEMENT

THIS AMENDMENT NO. 5 TO MERGER AND PURCHASE AGREEMENT (the "Fifth Amendment") is
made as of the 21st day of May, 1999, among Union Pacific Resources Company, a
Delaware corporation, Duke Energy Fuels, LP, now a wholly owned entity of Buyer,
and Duke Energy Field Services, Inc., a Colorado corporation.

         WHEREAS, the parties heretofore entered into a Merger and Purchase
Agreement dated November 20, 1998, which was amended by the Amendment No. 1
dated as of February 1, 1999, Amendment No. 2 dated as of March 5, 1999,
Amendment No. 3 dated as of March 30, 1999, and Amendment No. 4 dated as of
March 30, 1999 (collectively, the "Amended Agreement") (capitalized terms not
otherwise defined herein have the same meanings ascribed to such terms in the
Amended Agreement);

         WHEREAS, the parties hereto desire to amend the Amended Agreement as
described below by entering into this Fifth Amendment;

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements, representations, warranties, provisions and covenants herein
contained, the parties hereto hereby agree as follows:

         1. Schedule 7.08(a) and 7.08(d) are hereby amended and restated in
their entirety as attached hereto.

         2. This Fifth Amendment is executed, and shall be considered, as an
amendment to the Amended Agreement and shall form a part thereof, and the
provisions of the Amended Agreement, as amended by this Fifth Amendment, are
hereby ratified and confirmed in all respects.

         3. This Fifth Amendment may be executed in any number of counterparts,
each of which shall be deemed an original, and all of which taken together shall
constitute but one and the same instrument. This Agreement shall become binding
only when each party hereto has executed and delivered to the other parties one
or more counterparts.

         IN WITNESS WHEREOF, the parties hereto have duly executed this Fifth
Amendment or have caused this Fifth Amendment to be duly executed by their
respective authorized officers as of the day and year first written above.

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                              UNION PACIFIC RESOURCES COMPANY

                              By:      /s/ Joseph A. LaSala
                                 -------------------------------------------
                              Name:    Joseph A. LaSala
                              Title:   Vice President, General Counsel
                                       And Corporate Secretary

                              DUKE ENERGY FUELS, LP
                              By:  Fuels Holding Company Operating LLC
                              Its: General Partner

                              By: /s/ J.W. Mogg
                                 -------------------------------------------
                              Name:    J. W. Mogg
                              Title:   President and CEO

                              DUKE ENERGY FIELD SERVICES, INC.

                              By: /s/ J.W. Mogg
                                 -------------------------------------------
                              Name:    J. W. Mogg
                              Title:   President

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