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                          ASSIGNMENT AND ASSUMPTION AGREEMENT

         ASSIGNMENT AND ASSUMPTION AGREEMENT, dated as of May 28, 1998 (this
"ASSIGNMENT AGREEMENT"), by and between LONG ISLAND LIGHTING COMPANY, a New
York corporation ("LILCO"), MARKETSPAN TRADING SERVICES LLC, a New York
limited liability company formerly known as BL ENERGY MANAGEMENT LLC ("Energy
Manager") and MARKETSPAN CORPORATION, a New York corporation formerly known as
BL HOLDING CORP. ("MKT"), and acknowledged and agreed to by LONG ISLAND POWER
AUTHORITY, a corporate municipal instrumentality and political subdivision of
the State of New York ("LIPA") and LIPA ACQUISITION CORP., a New York
corporation and a wholly owned subsidiary of LIPA ("LIPA Sub").

                              W I T N E S S E T H

         WHEREAS, LIPA, LILCO, MKT and LIPA Sub are parties to that certain
Agreement and Plan of Merger, dated as of June 26, 1997 (the "Merger
Agreement");

         WHEREAS, in connection with the transactions contemplated by the
Merger Agreement, LIPA and LILCO entered into an Energy Management Agreement,
dated as of June 26, 1997 (as amended and supplemented up to and including the
Closing Date as therein defined, the "EMA"), Section 13.3 of which provided
that, effective upon the Closing Date, LILCO shall assign all of its rights,
obligations and interests thereunder to MKT or any affiliate thereof;

         WHEREAS, MKT hereby directs LILCO to assign to Energy Manager, its
wholly owned subsidiary, all rights, obligations and interests under the EMA
to be assigned pursuant to Section 13.3 thereof;

         WHEREAS, in connection with the Merger Agreement and in accordance
with the requirements of Section 13.3 of the EMA, MKT will, prior to the
Effective Time (as defined in the Merger Agreement), execute a Guaranty
Agreement, in substantially the form of the Guaranty Agreement attached to the
Merger Agreement as Exhibit E, pursuant to which MKT will, among other things,
guarantee the obligations of Energy Manager under the EMA;

         NOW THEREFORE, in consideration of the premises, the covenants and
agreements contained herein, and for other good and valuable consideration,
the receipt of which is hereby acknowledged, the parties hereto, intending to
be legally bound hereby, agree as follows:

  1 .     Definitions. Capitalized terms used herein and not otherwise defined
          herein have the respective meanings given in the Merger Agreement.

  2.      Assignment by LILCO to Energy Manager. Pursuant to the direction
          of MKT, LILCO hereby assigns to Energy Manager all of its rights,
          obligations and interests under the EMA.

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3.       Assumption of Liabilities and Obligations by Energy Manager.
         Energy Manager hereby agrees to assume all liabilities and obligations
         of LILCO under the EMA.

4.       Substitution of Energy Manager Where LILCO Appears. The EMA is hereby
         deemed amended, such that Energy Manager is substituted for LILCO as
         a named party, as the context may indicate, for all purposes under such
         Agreement and all references to LILCO in such Agreement shall be
         deemed to refer to Energy Manager.

5.       Acknowledgment by LIPA and LIPA Sub of Assumption, Assignment and
         Substitution. LIPA and LIPA Sub each hereby acknowledge and confirm
         that all of the liabilities, obligations, benefits and rights of
         LILCO under the EMA shall inure hereby to the benefit of Energy
         Manager under such Agreement.

6.       Counterparts. This Assignment Agreement may be executed in one or more
         counterparts, each of which shall be deemed to be an original, but
         all of which shall constitute one and the same agreement.

         IN WITNESS WHEREOF, LILCO, LIPA, LIPA Sub, MKT and Energy Manager
have caused this Assignment Agreement to be signed by their respective
officers thereunto duly authorized as of the date first written above.

  LONG ISLAND LIGHTING COMPANY             MARKETSPAN TRADING SERVICES LLC


  By: /s/ Leonard P. Novello               By: /s/ Joseph E. Fontana
      ----------------------------------       --------------------------------
      Name: Leonard P. Novello                 Name: Joseph E. Fontana
      Title: Senior Vice President/            Title: Vice President
             General Counsel


  MARKETSPAN CORPORATION

  By: /s/ Joseph E. Fontana
      ----------------------------------
      Name: Joseph E. Fontana
      Title: Vice President

  Acknowledged and Agreed to by:

  LONG ISLAND POWER AUTHORITY               LIPA ACQUISITION CORP.
  
  By: /s/ Seth Hulkower                     By: /s/ Seth Hulkower
      ----------------------------------       --------------------------------
      Name: Seth Hulkower                      Name: Seth Hulkower
      Title: Executive Director                Title: Executive Director

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