Document:

<PAGE>
                                                                  Exhibit 10.91

                            INSTRUMENT OF ASSUMPTION

         INSTRUMENT OF ASSUMPTION dated as of December 15, 1999, by MIDWEST
GENERATION, LLC, a Delaware limited liability company ("Purchaser"), in favor of
COMMONWEALTH EDISON COMPANY, an Illinois corporation ("ComEd"), and UNICOM
INVESTMENT INC., an Illinois corporation ("UII").

                              W I T N E SS E T H :

         WHEREAS, pursuant to the Asset Sale Agreement dated as of March 22,
1999 (as amended and/or assigned, the "Agreement") between Edison Mission
Energy, a California corporation, and ComEd and that certain Asset Sale
Agreement dated as of May 11, 1999 between ComEd and UII, ComEd and UII are
concurrently herewith selling, assigning, transferring, conveying and delivering
to Purchaser certain assets and properties defined in the Agreement as the
Assets; and

         WHEREAS, in partial consideration for such sale, assignment, transfer,
conveyance and delivery of the Assets, the Agreement requires Purchaser to
perform, pay or discharge certain obligations of ComEd, which are defined in the
Agreement as the Purchaser's Liabilities, by the execution and delivery to ComEd
and UII of this Instrument of Assumption;

         NOW, THEREFORE, pursuant to the terms of the Agreement and for good and
valuable consideration, Purchaser hereby assumes and undertakes and agrees to
perform, pay or discharge in accordance with the terms and conditions thereof,
all of the Purchaser's Liabilities (as defined in the Agreement).

         AND, for the consideration aforesaid, Purchaser for itself and its
successors and assigns has covenanted and by this instrument does covenant with
ComEd, UII and their respective successors and assigns that Purchaser and its
successors and assigns will do, execute and deliver, or will cause to be done,
executed and delivered, all such further acts, transfers, assignments and
conveyances, powers of attorney and assurances for the better assuming from
ComEd, UII and their respective successors and assigns all of the Purchaser's
Liabilities as ComEd, UII and their respective successors or assigns shall
reasonably require.

         Capitalized terms used herein without definition shall have the
respective meanings ascribed to such terms in the Agreement.

<PAGE>

         This Instrument of Assumption shall inure to the benefit of and be
binding upon the successors and assigns of ComEd and UII and the successors and
assigns of Purchaser.

                                       MIDWEST GENERATION, LLC

                                       By:   /s/ Georgia Nelson
                                             ------------------------<PAGE>

                                                                   Exhibit 10.92

                                                                  Exhibit E-1 to
                                                         Intercreditor Agreement

                                                                  EXECUTION COPY

================================================================================

                             SUBORDINATION AGREEMENT

                          dated as of December 15, 1999

                                  by and among

                                 CITIBANK, N.A.,
                          as Holdings Collateral Agent

                           EDISON MISSION OVERSEAS CO.

                                       and

                             MIDWEST GENERATION, LLC

================================================================================

<PAGE>

                             SUBORDINATION AGREEMENT

                  This SUBORDINATION AGREEMENT, dated as of December 15, 1999
(this "AGREEMENT"), is by and between CITIBANK, N.A., as Holdings Collateral
Agent (as defined in the Intercreditor Agreement referred to below), EDISON
MISSION OVERSEAS CO., a Delaware corporation ("OVERSEAS"), and MIDWEST
GENERATION, LLC, a Delaware limited liability company ("MIDWEST").

                                    RECITALS

                  WHEREAS, Edison Mission Midwest Holdings Co. ("HOLDINGS") has
entered into the Credit Agreement, dated as of December 15, 1999 (the "HOLDINGS
CREDIT AGREEMENT"), with certain commercial lending institutions party thereto
(the "HOLDINGS LENDERS") and The Chase Manhattan Bank, as Administrative Agent
for the Holdings Lenders, pursuant to which the Holdings Lenders have agreed to
make loans (the "HOLDINGS LOANS") to Holdings from time to time on the terms and
subject to the conditions contained in the Holdings Credit Agreement;

                  WHEREAS, Holdings has entered into Collateral Agency and
Intercreditor Agreement, dated as of December 15, 1999 (the "INTERCREDITOR
AGREEMENT"), among Midwest Generation EME, LLC, Holdings, Overseas, Midwest,
Collins Holdings EME, LLC, the Owner Lessors (as such term is defined therein),
Midwest Funding LLC, the Holdings Administrative Agent (as such term is defined
therein), each Holder Representative (as such term is defined therein) each
Other Representative (as such term is defined therein), the Midwest LC Issuer
(as such term defined therein), the Depositary Agent (as such term is defined
therein), the Depositary Bank (as such term is defined therein) and the Holdings
Collateral Agent (as such term is defined therein);

                  WHEREAS, Overseas is a wholly-owned subsidiary of Holdings and
Holdings has agreed to make an equity contribution (the "HOLDINGS EQUITY
CONTRIBUTION") to Overseas;

                  WHEREAS, Midwest has entered into the Subordinated Loan
Agreement, dated as of December 15, 1999 (the "FINANCE LOAN AGREEMENT"), with
Overseas, pursuant to which Overseas has agreed to make a loan (the "FINANCE
LOAN") to Midwest on the terms and subject to the conditions contained in the
Finance Loan Agreement;

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                  WHEREAS, Midwest has entered into the Subordinated Revolving
Loan Agreement, dated as of December 15, 1999 (the "REVOLVING LOAN AGREE MENT"),
with Overseas, pursuant to which Overseas has agreed to make loans (the
"REVOLVING LOANS") to Midwest to from time to time on the terms and subject to
the conditions contained in the Revolving Loan Agreement;

                  WHEREAS, the parties hereto would like to subordinate the
Finance Loan and the Revolving Loans, and all other obligations of Midwest under
the Finance Loan Agreement and the Revolving Loan Agreement, respectively, to
the guarantee by Midwest of the Obligations of Holdings under the Holdings
Credit Agreement and the Holdings Credit Documentation; and

                  WHEREAS, the execution and delivery of this Agreement is a
condition precedent to the effectiveness of the Holdings Credit Agreement and
the making by the Holdings Lenders of Holdings Loans to Holdings thereunder.

                                    AGREEMENT

                  NOW, THEREFORE, in consideration of the foregoing, and for
other good and valuable consideration, the receipt and adequacy of which are
hereby acknowledged, the parties hereto agree as follows:

                                    ARTICLE I
                  DEFINITIONS; PRINCIPLES OF CONSTRUCTION

                  Section 1.1  DEFINITIONS.

                           (a) HOLDINGS CREDIT AGREEMENT. Unless otherwise
expressly provided herein, capitalized terms used but not defined in this
Agreement shall have the meanings given to such terms in the Holdings Credit
Agreement.

                           (b) OTHER DEFINED TERMS. The following terms, when
used herein, shall have the following meanings:

                           "BORROWER" shall mean Midwest.

                           "PROCEEDING" shall have the meaning given to such
         term in SECTION 3.2.

                                        3

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                           "SENIOR CLAIMS" shall have the meaning given to such
         term in SECTION 2.1(a).

                           "SUBORDINATED CLAIMS" shall have the meaning given to
         such term in SECTION 2.1(a).

                           "SUBORDINATED NOTES" shall have the meaning given to
         such term in SECTION 2.1(c).

                           "SUBORDINATED PARTY" shall mean Overseas in its
         capacity as lender under the Finance Loan Agreement and as lender under
         the Revolving Loan Agreement.

                  Section 1.2 PRINCIPLES OF CONSTRUCTION. Unless otherwise
expressly provided herein, the principles of construction set forth in the
Holdings Credit Agreement shall apply to this Agreement.

                                   ARTICLE II
                            SUBORDINATION PROVISIONS

                  Section 2.1 SUBORDINATION OF FINANCE LOAN AND REVOLVING LOANS.
Until all Obligations shall have been indefeasibly paid in full and all
Commitments shall have been terminated:

                           (a) all principal of, premium, if any, and interest
owing on the Finance Loan or any Revolving Loan made by Overseas, and any and
all other indebtedness and obligations of Borrower to Overseas, whether direct
or indirect, absolute or contingent, due or to become due, or now existing or
hereafter incurred or created (collectively, the "SUBORDINATED CLAIMS") shall be
subordinate, to the extent and in the manner hereinafter set forth, to the prior
payment of, and junior in right of payment of any and all obligations whether
now existing or hereafter incurred or created of Borrower to the Secured Parties
(collectively, the "SENIOR CLAIMS");

                           (b) Borrower shall not, directly or indirectly, make
any regularly scheduled payment of principal or interest on account of, or
transfer any collateral for any part of, any Subordinated Claims; PROVIDED,
HOWEVER, that Borrower may make regularly scheduled payments of interest and
principal on account of Subordinated Claims if no Event of Default exists in
respect of the Holdings Credit Agreement;

                                        4

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                           (c) the Subordinated Party shall not demand, sue for
or accept from Borrower or any other Person any payment or collateral in respect
of any Subordinated Claims, or take any other action to enforce their rights or
exercise any remedies in respect of any Subordinated Claims (whether upon the
occurrence or during the continuation of an event of default under the Finance
Loan Agreement or the Revolving Loan Agreement, as applicable, or an event of
default under any promissory notes evidencing Subordinated Claims (collectively,
"SUBORDINATED NOTES") or otherwise), or cancel, set off or otherwise discharge
any part of any Subordinated Claims; and

                           (d) neither Borrower nor the Subordinated Party shall
otherwise take any action prejudicial to or inconsistent with the priority
position of the Secured Parties over the Subordinated Party created by this
SECTION 2.1.

                  Section 2.2 RELIANCE. All Senior Claims shall conclusively be
deemed to have been created, contracted or incurred in reliance on the
subordination provisions contained in this Agreement and all dealings between
Borrower and each of the holders of Senior Claims shall be deemed to have been
consummated in reliance upon the subordination provisions contained herein.

                  Section 2.3 OTHER HOLDERS. The subordination provisions set
forth in this Agreement shall be binding upon transferees or assignees of the
Subordinated Party and upon each other holder of Subordinated Claims and shall
inure to the benefit of transferees or assignees of the Secured Parties and
every other holder of Senior Claims.

                                   ARTICLE III
                              WRONGFUL COLLECTIONS

                  Section 3.1 TURNOVER. Should any payment on account of, or any
collateral for any part of, any Subordinated Claims be received by the
Subordinated Party in violation of this Agreement, such payment or collateral
shall be delivered forthwith to the Holdings Collateral Agent for application in
accordance with the Holdings Credit Agreement and the Loan Documents. The
Holdings Collateral Agent is irrevocably authorized to supply any required
endorsement or assignment which may have been omitted. Until so delivered, any
such payment or collateral shall be held by the Subordinated Party in trust for
the Secured Parties and shall not be commingled with other funds or property of
the Subordinated Party.

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<PAGE>

                  Section 3.2 SURVIVAL OF OBLIGATION. The obligation of the
Subordinated Party to deliver to the Holdings Collateral Agent any payment or
collateral received in connection with any Subordinated Claims, as set forth in
SECTION 3.1, shall survive and shall not be in any way affected by the result of
any (a) insolvency, bankruptcy, receivership, liquidation, reorganization,
readjustment, composition or other similar proceeding relating to Borrower, its
property or its creditors as such, (b) proceeding for any liquidation,
dissolution or other winding-up of Borrower, voluntary or involuntary, whether
or not involving insolvency or bankruptcy proceedings, (c) assignment for the
benefit of creditors, (d) other marshalling of the assets of Borrower or (e)
general meeting of creditors of Borrower, in each case, under the laws of the
United States or any other jurisdiction (any such event, a "PROCEEDING").

                                   ARTICLE IV
                                   PROCEEDINGS

                  Section 4.1 COMMENCEMENT OF PROCEEDINGS. The Subordinated
Party shall not commence, or join with any other creditor or creditors of
Borrower in commencing, any Proceeding against Borrower.

                  Section 4.2 PAYMENTS AND DISTRIBUTIONS. In the event of any
Proceeding, until all Obligations shall have been indefeasibly paid in full and
all Commit ments shall have been terminated, any payment or distribution of any
kind or charac ter, whether in cash, property or securities, which, but for the
subordination provi sions of this Agreement would otherwise be payable or
deliverable upon or in respect of Subordinated Claims, shall instead be paid
over or delivered to the Holdings Collateral Agent in accordance with ARTICLE
III and no holder of Subordinated Claims shall receive any such payment or
distribution or any benefit therefrom.

                  Section 4.3 ENFORCEMENT OF SUBORDINATED CLAIMS.

                           (a) ENFORCEMENT BY THE SECURED PARTIES. At any
Proceeding, until all Obligations shall have been indefeasibly paid in full and
all Commitments shall have been terminated, the Secured Parties are hereby
irrevocably authorized (but not required) to:

                                        6

<PAGE>

                           (i) enforce claims comprising Subordinated Claims in
         the name of the Subordinated Party by proof of debt, proof of claim,
         suit or otherwise;

                           (ii) collect any assets of Borrower distributed,
         divided or applied by way of dividend or payment, and any securities
         issued, in each case, on account of Subordinated Claims and apply the
         same, or the proceeds of any realization upon the same that the Secured
         Parties in their discretion elect to effect, to Senior Claims until all
         Obligations shall have been indefeasibly paid in full and all
         Commitments shall have been terminated; PROVIDED, HOWEVER, that the
         Secured Parties shall render any surplus to the Subordinated Party or
         its Affiliates, as their interests appear, or interplead such surplus
         with a court of competent jurisdiction;

                           (iii) vote claims comprising Subordinated Claims to
         accept or reject any plan of partial or complete liquidation,
         reorganization, arrangement, composition or extension; and

                           (iv) take generally any action in connection with any
         such Proceeding which the Subordinated Party might otherwise take.

                           (b) COOPERATION. The Subordinated Party shall
cooperate fully with the Secured Parties and perform all acts requested by the
Secured Parties to enable the Secured Parties to enforce any Subordinated Claims
pursuant to clause (a) above, including, without limitation, filing appropriate
proofs of claim and executing and delivering all necessary powers of attorney,
assignments or other instruments.

                           (c) ENFORCEMENT BY THE SUBORDINATED PARTY.  After the
commencement of any Proceeding, the Subordinated Party may inquire in writing of
the Secured Parties whether the Secured Parties intend to exercise their rights
set forth in clause (a) above with respect to any Subordinated Claims. Should
the Secured Parties fail, within a reasonable time after receipt of such
inquiry, either to file a proof of claim with respect to any Subordinated Claims
and to furnish a copy thereof to the Subordinated Party, or to inform the
Subordinated Party in writing that the Secured Parties intend to exercise their
rights to assert such Subordinated Claims in the manner provided in clause (a)
above, the Subordinated Party may (but shall not be required to) proceed to file
a proof of claim with respect to such Subordinated

                                        7

<PAGE>

Claims and take such further steps with respect thereto, not inconsistent with
this Agreement, as the Subordinated Party may deem proper.

                           (d) SUBROGATION. The Subordinated Party shall not
have any subrogation or other rights as a holder of Senior Claims, and the
Subordinated Party hereby irrevocably waives all such rights of subrogation and
all rights of reimbursement or indemnity whatsoever and all rights of recourse
to any security for any Senior Claims, until such time as all Obligations shall
have been indefeasibly paid in full and all Commitments shall have been
terminated. Subject to and from and after the payment in full of all Obligations
and the termination of all Commitments, the Subordinated Party shall be
subrogated to any rights of the Secured Parties to receive payments or
distributions of cash, property or securities of Borrower applicable to any
Subordinated Claims until all amounts owing on such Subordinated Claims shall be
paid in full.

                                    ARTICLE V
                              LIMITATION ON ACTIONS

                  Section 5.1 ACTIONS PROHIBITED. Until all Obligations shall
have been indefeasibly paid in full and all Commitments shall have been
terminated, the Subordinated Party shall not, without the prior written consent
of the Secured Parties:

                           (a) take, obtain or hold (or permit anyone acting on
its behalf to take, obtain or hold) any assets of Borrower, whether as a result
of any admin istrative, legal or equitable action, or otherwise, in violation of
the subordination provisions contained in this Agreement;

                           (b)  accelerate payment of any Subordinated Claims or
otherwise require such Subordinated Claims to be paid prior to their stated or
scheduled maturity date;

                           (c) commence, prosecute or participate in (i) any
administra tive, legal or equitable action against or involving Borrower
relating to any Subordi nated Claims, including, without limitation, any
Proceeding, or (ii) any administra tive, legal or equitable action to (a)
enforce or collect any judgment obtained in re spect of any Subordinated Claims,
(b) enforce or exercise remedies arising under or pursuant to any Subordinated
Claims, (c) enforce or exercise remedies under or pursuant to any lien or other
security interest securing any Subordinated

                                        8

<PAGE>

Claims or (d) enforce or exercise remedies with respect to any covenant,
agreement, representation or other undertaking contained in any Subordinated
Notes; or

                           (d) exercise any other rights or remedies to enforce
any Subordinated Claims, any collateral security provided with respect to such
Subordinated Claims or any covenant, agreement, representation or other
undertaking contained in any Subordinated Notes.

                  Section 5.2 DEFENSE IN ACTION. If the Subordinated Party, in
violation of the provisions herein set forth, shall commence, prosecute or
participate in any suit, action, case or Proceeding referred to in SECTION 5.1,
Borrower may interpose as a defense or plea the provisions set forth herein, and
any holder of any Senior Claims may intervene and interpose such defense or plea
in its own name or in the name of Borrower, and shall, in any event, be entitled
to restrain the enforcement of the provisions of any Subordinated Claims in its
own name or in the name of Borrower, as the case may be, in the same suit,
action, case or Proceeding or in any independent suit, action, case or
Proceeding.

                                   ARTICLE VI
                             SUBORDINATION ABSOLUTE

                  Section 6.1 SURVIVAL OF RIGHTS. The rights under this
Agreement of the holders of Senior Claims as against the Subordinated Party
shall remain in full force and effect without regard to, and shall not be
impaired or affected by:

                           (a) any act or failure to act on the part of
Borrower;

                           (b) any extension or indulgence in respect of any
payment or prepayment of any Senior Claims or any part thereof or in respect of
any other amount payable to any holder of any Senior Claims;

                           (c) any amendment, modification or waiver of, or
addition or supplement to, or deletion from, or compromise, release, consent or
other action in respect of, any of the terms of any Senior Claims or the Loan
Documents;

                           (d) (i) any exercise or non-exercise by the holder of
any Senior Claims of any right, power, privilege or remedy under or in respect
of such Senior Claims, the Loan Documents or the subordination provisions
contained herein, (ii) any waiver by the holder of any Senior Claims of any
right, power, privilege

                                       9
<PAGE>

or remedy or of any default in respect of such Senior Claims, the Loan
Documents or the subordination provisions contained herein or (iii) any
receipt by the holder of any Senior Claims or any failure by such holder to
perfect a security interest in, or any release by such holder of, any
security for the payment of such Senior Claims;

                           (e) any merger or consolidation of Borrower or any of
its subsidiaries into or with other Person, or any sale, lease or transfer of
any or all of the assets of Borrower or any of its subsidiaries to any other
Person;

                           (f) any payment or other distribution to any holder
of any Senior Claims in any Proceeding;

                           (g) absence of any notice to, or knowledge by, the
Subordi nated Party of the existence or occurrence of any of the matters or
events set forth in the foregoing clauses (a) through (f); or

                           (h) any other circumstance.

                  Section 6.2  WAIVERS.

                           (a) WAIVER OF DEFENSES. The Subordinated Party hereby
irrevocably waives, in any proceeding by the Secured Parties to enforce their
rights under this Agreement, (i) any defense based on the adequacy of a remedy
at law which might be asserted as a bar to the remedy of specific performance of
this Agreement and (ii) the defense that claims asserted by the Secured Parties
pursuant to this Agreement are RES JUDICATA as a result of any decision rendered
in any prior Proceeding.

                           (b) OTHER WAIVERS. The Subordinated Party hereby
irrevoca bly waives (i) notice of any of the matters referred to in SECTION 6.1,
(ii) all notices which may be required, whether by statute, rule of law or
otherwise, to preserve intact any rights of any holder of any Senior Claims
against Borrower, including, without limitation, any demand, presentment and
protest, or any proof of notice of nonpayment under any document evidencing such
Senior Claims or under the Loan Documents, (iii) notice of the acceptance of or
reliance on this Agreement by the Secured Parties, (iv) notice of any renewal,
extension or accrual of any Senior Claims, or any loans made or other action
taken in reliance on this Agreement, (v) any right to the enforcement, assertion
or exercise by any holder of any Senior

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Claims of any right, power, privilege or remedy conferred in any document
evidencing such Senior Claims or in the Loan Documents, or otherwise, (vi) any
requirement of diligence on the part of any holder of any Senior Claims, (vii)
any requirement on the part of any holder of any Senior Claims to mitigate
damages resulting from any default under any documents evidencing such Senior
Claims or under the Loan Documents and (viii) any notice of any sale, transfer
or other disposition of any Senior Claims by any holder thereof.

                  Section 6.3 ASSENT. The Subordinated Party hereby irrevocably
assents to (a) any renewal, extension or postponement of the time of payment of
any Senior Claims or any other indulgence with respect thereto, (b) any increase
in the amount of any Senior Claims, (c) any substitution, exchange or release of
collateral for any Senior Claims, (d) the addition or release of any Person
primarily or secondarily liable for any Senior Claims and (e) the provisions of
any instrument, security or other writing evidencing any Senior Claims.

                                   ARTICLE VII
                              BORROWER OBLIGATIONS

                  The provisions of this Agreement are intended solely for the
purpose of defining the relative rights and obligations of the Subordinated
Party and the Secured Parties. Nothing contained herein (a) is intended to or
shall impair, as among Borrower, its creditors and the Subordinated Party, the
obligation of Borrower, which is absolute and unconditional, to pay to the
Subordinated Party, as and when the same shall become due and payable in
accordance with its terms, all amounts payable in respect of any Subordinated
Claims, or (b) is intended to affect the relative rights of the Subordinated
Party and creditors of Borrower other than the Secured Parties.

                                  ARTICLE VIII
                            MISCELLANEOUS PROVISIONS

                  Section 8.1  WAIVERS, AMENDMENTS.

                           (a) The provisions of this Agreement may from time to
time be amended, modified or waived, if such amendment, modification or waiver
is in writing and consented to by each of the parties hereto.

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                           (b) No failure or delay in exercising any power or
right under this Agreement shall operate as a waiver thereof, nor shall any
single or partial exercise of any such power or right preclude any other or
further exercise thereof or the exercise of any other power or right. No notice
to or demand on any party in any case shall entitle it to any notice or demand
in similar or other circumstances. No waiver or approval under this Agreement
shall, except as may be otherwise stated in such waiver or approval, be
applicable to subsequent transactions. No waiver or approval hereunder shall
require any similar or dissimilar waiver or approval thereafter to be granted
hereunder.

                  Section 8.2 NOTICES. All notices and other communications
provided to any party hereto under this Agreement shall be in writing or by
facsimile and addressed, delivered or transmitted to such party at its address
or facsimile number set forth below or at such other address or facsimile number
as may be designated by such party in a written notice to the other parties:

              Holdings
              Collateral Agent:      Citibank, N.A.
                                     111 Wall Street
                                     5th Floor, Zone 2
                                     New York, NY 10005
                                     Facsimile:  (212) 657-3866
                                     Attention:  Global Trust & Agency Services

              Overseas:              Edison Mission Overseas Co.
                                     1209 Orange Street
                                     Wilmington, DE   19890
                                     Facsimile: (302) 674-8340
                                     Attention:  General Counsel

                                     COPY TO:
                                     Edison Mission Energy
                                     18101 Von Karman Avenue
                                     Suite 1700
                                     Irvine, CA  92612-1046
                                     Facsimile:  (949) 476-2378
                                     Attention:  General Counsel

              Midwest:               Midwest Generation, LLC

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<PAGE>

                                     One Financial Place
                                     440 South LaSalle Street
                                     Suite 3500
                                     Chicago, IL  60605
                                     Facsimile:  (312) 583-6111
                                     Attention:  Georgia Nelson

                                     COPY TO:
                                     Edison Mission Energy
                                     18101 Von Karman Avenue
                                     Suite 1700
                                     Irvine, CA  92612-1046
                                     Facsimile:  (949) 476-2378
                                     Attention:  General Counsel

Any notice, if mailed and properly addressed with postage prepaid shall be
effective five (5) Business Days after being sent or if properly addressed and
sent by pre-paid courier service, shall be deemed given when received; any
notice, if transmitted by facsimile, shall be deemed given when transmitted (if
confirmed).

                  Section 8.3 SEVERABILITY. Any provision of this Agreement
which is prohibited or unenforceable in any jurisdiction shall, as to such
provision and such jurisdiction, be ineffective to the extent of such
prohibition or unenforceability without invalidating the remaining provisions of
this Agreement or affecting the validity or enforceability of such provision in
any other jurisdiction.

                  Section 8.4 HEADINGS. The various headings of this Agreement
are inserted for convenience only and shall not affect the meaning or
interpretation of this Agreement or any provisions hereof or thereof.

                  Section 8.5 EXECUTION IN COUNTERPARTS, EFFECTIVENESS. This
Agree ment may be executed by the parties hereto in several counterparts, each
of which shall be deemed to be an original and all of which shall constitute
together but one and the same agreement.

                  Section 8.6 GOVERNING LAW; ENTIRE AGREEMENT. THIS AGREEMENT
SHALL BE DEEMED TO BE A CONTRACT MADE UNDER AND GOVERNED BY THE LAWS OF THE
STATE OF NEW YORK. This Agreement constitutes the entire understanding among the
parties hereto with respect to

                                                 13

<PAGE>

the subject matter hereof and supersede any prior agreements, written or oral,
with respect thereto.

                  Section 8.7 SUCCESSORS AND ASSIGNS. This Agreement shall be
binding upon and shall inure to the benefit of the parties hereto and their
respective successors and assigns.

                  Section 8.8  FORUM SELECTION AND CONSENT TO JURISDICTION.
ANY LITIGATION BASED HEREON, OR ARISING OUT OF, UNDER, OR IN CONNECTION WITH,
THIS AGREEMENT, OR ANY COURSE OF CONDUCT, COURSE OF DEALING, STATEMENTS
(WHETHER VERBAL OR WRITTEN) OR ACTIONS OF ANY PARTY HERETO SHALL BE BROUGHT
AND MAINTAINED EXCLUSIVELY IN THE COURTS OF THE STATE OF NEW YORK OR IN THE
UNITED STATES DISTRICT COURT FOR THE SOUTHERN DISTRICT OF NEW YORK. EACH
PARTY HERETO HEREBY EXPRESSLY AND IRREVOCABLY SUBMITS TO THE JURISDICTION OF
THE COURTS OF THE STATE OF NEW YORK AND OF THE UNITED STATES DISTRICT COURT
FOR THE SOUTHERN DISTRICT OF NEW YORK FOR THE PURPOSE OF ANY SUCH LITIGATION
AS SET FORTH ABOVE AND IRREVOCABLY AGREES TO BE BOUND BY ANY JUDGMENT
RENDERED THEREBY IN CONNECTION WITH SUCH LITIGATION. EACH PARTY HERETO
FURTHER IRREVOCABLY CONSENTS TO THE SERVICE OF PROCESS BY REGISTERED MAIL,
POSTAGE PREPAID, OR BY PERSONAL SERVICE WITHIN OR WITHOUT THE STATE OF NEW
YORK. EACH PARTY HERETO HEREBY EXPRESSLY AND IRREVOCABLY WAIVES, TO THE
FULLEST EXTENT PERMITTED BY LAW, ANY OBJECTION WHICH IT MAY HAVE OR HEREAFTER
MAY HAVE TO THE LAYING OF VENUE OF ANY SUCH LITIGATION BROUGHT IN ANY SUCH
COURT REFERRED TO ABOVE AND ANY CLAIM THAT ANY SUCH LITIGATION HAS BEEN
BROUGHT IN AN INCONVENIENT FORUM. TO THE EXTENT THAT ANY PARTY HERETO HAS OR
HEREAFTER MAY ACQUIRE ANY IMMUNITY FROM JURISDICTION OF ANY COURT OF FROM ANY
LEGAL PROCESS (WHETHER THROUGH SERVICE OR NOTICE, ATTACHMENT PRIOR TO
JUDGMENT, ATTACHMENT IN AID OF EXECUTION OR OTHERWISE) WITH RESPECT TO ITSELF
OR ITS PROPERTY, SUCH PARTY HEREBY IRREVOCABLY WAIVES SUCH IMMUNITY IN
RESPECT OF ITS OBLIGATIONS UNDER THIS AGREEMENT.

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                  Section 8.9 WAIVER OF JURY TRIAL. EACH PARTY HEREBY KNOW
INGLY, VOLUNTARILY AND INTENTIONALLY WAIVES ANY RIGHTS IT MAY HAVE TO A TRIAL BY
JURY IN RESPECT OF ANY LITIGATION BASED HEREON, OR ARISING OUT OF, UNDER, OR IN
CONNECTION WITH, THIS AGREEMENT, OR ANY COURSE OF CONDUCT, COURSE OF DEALING,
STATEMENTS (WHETHER VERBAL OR WRITTEN) OR ACTIONS OF ANY PARTY HERETO. EACH
PARTY ACKNOWLEDGES AND AGREES THAT IT HAS RECEIVED FULL AND SUFFICIENT
CONSIDERATION FOR THIS PROVISION AND THAT THIS PROVISION IS A MATERIAL INDUCE
MENT FOR THE OTHER PARTIES ENTERING INTO THIS AGREEMENT.

                                       15

<PAGE>

                  IN WITNESS WHEREOF, the parties hereto have caused this
Subordination Agreement to be executed by their respective officers as of the
days and year first above written.

                            CITIBANK, N.A.,
                            as Holdings Collateral Agent,

                            By:      /s/ Jenny Cheng
                                     ---------------------------
                                     Name: Jenny Cheng
                                     Title: Vice President

                            EDISON MISSION OVERSEAS CO.

                            By:      /s/ John P. Finneran, Jr.
                                     -----------------------------
                                     Name: John P. Finneran, Jr.
                                     Title: Vice President

                            MIDWEST GENERATION, LLC

                            By:      /s/ John P. Finneran, Jr.
                                     ------------------------------
                                     Name: John P. Finneran, Jr.
                                     Title: Vice President

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