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                                                                   EXHIBIT 10.21




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                              SEVENTH SUPPLEMENT TO

                              INTER-GROUP AGREEMENT

                                between and among

                                   AT&T CORP.,

                                on the one hand,

                                       and

                           LIBERTY MEDIA CORPORATION,

                             LIBERTY MEDIA GROUP LLC

                      and each Covered Entity listed on the

                             signature pages hereof,

                               on the other hand,

                            dated as of July 25, 2000



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                              SEVENTH SUPPLEMENT TO

                              INTER-GROUP AGREEMENT

                  Agreement dated as of July 25, 2000 (this "Agreement") between
AT&T Corp., a New York corporation ("AT&T"), for itself and on behalf of the
members of the Common Stock Group, on the one hand, and Liberty Media
Corporation, a Delaware corporation ("LMC"), Liberty Media Group LLC, a Delaware
limited liability company, and for so long as such Covered Entity remains a
Covered Entity under the applicable provisions of the AT&T Charter Amendment,
each Covered Entity listed on the signature pages hereof (collectively, the
"Liberty Media Parties"), for themselves and, in the case of LMC, on behalf of
the other members of the Liberty Media Group, on the other hand.

                  WHEREAS, AT&T and the Liberty Media Parties are parties to
that certain Inter-Group Agreement, dated as of March 9, 1999 (the "Inter-Group
Agreement"), as supplemented and modified by (i) the First Supplement to
Inter-Group Agreement, dated as of May 28, 1999, as such First Supplement has
been amended (the "First Supplement"), (ii) the Second Supplement to Inter-
Group Agreement, dated as of September 24, 1999 (the "Second Supplement"), (iii)
the Third Supplement to Inter-Group Agreement, dated as of October 20, 1999 (the
"Third Supplement", (iv) the Fourth Supplement to Inter-Group Agreement, dated
as of December 6, 1999 (the "Fourth Supplement"), (v) the Fifth Supplement to
Inter-Group Agreement, dated as of December 10, 1999 (the "Fifth Supplement")
and (vi) the Sixth Supplement to Inter-Group Agreement, dated as of December 30,
1999 (the "Sixth Supplement"), which establishes certain terms and conditions
concerning the responsibilities and obligations of each Group to the other as
well as certain additional provisions concerning the Groups' relationships with
each other;


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                  WHEREAS, AT&T, E-Group Merger Corp., a Delaware corporation
("Merger Sub E"), LMC and Video Services Corporation, a Delaware corporation
("VSC"), intend to enter into an Agreement and Plan of Merger, dated as of July
25, 2000 (the "VSC Merger Agreement"), pursuant to which, among other things,
subject to the terms and conditions contained in the VSC Merger Agreement,
Merger Sub E will be merged with and into VSC, with VSC as the surviving entity
in the merger (the "VSC Merger");

                  WHEREAS, in connection herewith, AT&T, LMC and certain of
their respective affiliates are also entering into an Eighth Amendment to Tax
Sharing Agreement (the "Eighth Tax Sharing Amendment"), dated as of the date
hereof, which amends that certain Tax Sharing Agreement, dated as of March 9,
1999, as amended (the "Tax Sharing Agreement"), to which AT&T, LMC and certain
of their respective affiliates are parties;

                  WHEREAS, LMC has requested in writing that AT&T enter into the
VSC Merger Agreement, this Agreement and the Eighth Tax Sharing Agreement and
consummate the transactions contemplated thereby;

                  WHEREAS, as a condition to the willingness of each of AT&T and
LMC to enter into the VSC Merger Agreement, AT&T and the Liberty Media Parties
have determined to enter into this Agreement and the Eighth Tax Sharing
Amendment;

                  WHEREAS, AT&T and the Liberty Media Parties desire to
supplement and modify the Inter-Group Agreement in the manner set forth in this
Agreement and to establish in this Agreement certain terms and conditions
concerning the responsibilities and obligations of each


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Group to the other as well as certain additional provisions concerning each
Group's relationship with each other as the same may relate to the VSC Merger,
and certain related transactions;

                  WHEREAS, in connection herewith, the Capital Stock Committee
has adopted the resolutions attached as Exhibit A.

                  NOW, THEREFORE, in consideration of the foregoing and the
mutual covenants and agreements contained herein, and intending to be legally
bound hereby, AT&T and the Liberty Media Parties hereby agree as follows:

                                    ARTICLE I

                     OBLIGATIONS RELATING TO THE VSC MERGER

                  SECTION 1.1. Post-Closing Contribution. As soon as reasonably
practicable following the effectiveness of the VSC Merger, each of LMC and AT&T
shall use all reasonable efforts to engage in the Post-Merger Restructuring
Transactions, in each case, to the extent then permitted by law. Each of AT&T
and LMC shall take, and AT&T shall cause each of its Subsidiaries to take, any
and all required actions (whether as a stockholder (or other interest holder) or
through its respective representatives on the board of directors (or comparable
governing body) of the applicable entity), to give effect to the previous
sentence.

                  SECTION 1.2. Certain Liabilities Relating to the VSC Merger.

                  (a) Subject to the last sentence of this subsection (a), as
between the Common Stock Group and the Liberty Media Group, all of the following
Liabilities shall be Liabilities of the Liberty Media Group:

                  (i)      all Liabilities of VSC and any of its subsidiaries
                           and affiliates (and, in each case, any predecessors
                           or successors thereto);


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                  (ii)     all Liabilities arising out of or related to the VSC
                           Merger Agreement and the transactions contemplated
                           thereby, including (A) all Liabilities arising out of
                           or relating to any breach of the VSC Merger Agreement
                           by LMC or VSC, whether such breach is of a
                           representation, warranty, agreement or obligation
                           made to AT&T, LMC or otherwise, and without reference
                           to any qualification of any such representation,
                           warranty, agreement or obligation by reference to
                           materiality or the Company Disclosure Schedule, and
                           without reference to any limitation on survival of
                           such representation, warranty, covenant or obligation
                           set forth in the VSC Merger Agreement, (B) any
                           Liabilities to third parties contemplated by Section
                           4.12 of the VSC Merger Agreement, (C) all Liabilities
                           required to carry out the provisions of Sections 2.1,
                           2.2, 2.3, 2.4, 2.5 and 2.6 of the VSC Merger
                           Agreement and all other Liabilities relating to the
                           issuance of any securities of Parent or any of its
                           Subsidiaries arising as a result of the transactions
                           contemplated by the VSC Merger Agreement, (D) all
                           Liabilities under Section 3.6 of the VSC Merger
                           Agreement, (E) all Liabilities arising out of or
                           related to any registration rights granted by VSC (it
                           being agreed that AT&T is not responsible for and is
                           not assuming any such obligation and shall not be
                           required to register any AT&T Liberty Tracking Shares
                           or shares of Parent Common Stock pursuant to any
                           registration rights agreement related to VSC or the
                           holders of any securities of VSC, other than the
                           registration of the Merger Consideration pursuant to
                           the Registration Statement, as provided in the VSC
                           Merger


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                           Agreement), (F) all Liabilities arising out of or
                           related to Section 7.10 of the Merger Agreement, (G)
                           all Liabilities arising out of or related to any
                           lawsuit brought, proposed or threatened against AT&T
                           or Merger Sub E in connection with the execution,
                           delivery or performance of the VSC Merger Agreement
                           or this Agreement by AT&T or Merger Sub E, by any
                           third party other than VSC, it being understood that
                           all Liabilities arising out of or related to any such
                           lawsuit brought, proposed or threatened by VSC shall
                           be the Liabilities of the Liberty Media Group if such
                           lawsuit relates to any action or omission that (1) is
                           not (or under this Agreement would be deemed not to
                           be) a violation of the VSC Merger Agreement or this
                           Agreement or (2) otherwise was taken, or omitted to
                           be taken, at the request or direction of any member
                           of the Liberty Media Group, including any issuance of
                           or failure to issue Class A Liberty Group Stock
                           (regardless of whether any such issuance would be in
                           excess of the number of shares of Class A Liberty
                           Group Stock that are authorized but not issued or
                           reserved for issuance), and (H) any Liabilities
                           required to be incurred to relieve AT&T and any
                           member of the Common Stock Group of any Liability or
                           obligation that binds or is enforceable against AT&T
                           or such member of the Common Stock Group as a result
                           of any agreement between VSC or any of its
                           Subsidiaries, on the one hand, and any other Person,
                           on the other hand (other than any such agreement
                           executed by AT&T or a member of the Common Stock
                           Group);


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                  (iii)    all Liabilities arising out of the consummation of
                           the VSC Merger or any of the transactions
                           contemplated thereby, including the Post-Merger
                           Restructuring Transactions and any other transaction
                           contemplated by this Agreement or the VSC Merger
                           Agreement, notwithstanding the failure to receive any
                           consent, approval or authorization, or any failure to
                           make any filing or notification, from or to any
                           Person that may be required in connection therewith;

                  (iv)     all Liabilities arising out of the consummation of,
                           or failure to consummate, the Post-Merger
                           Restructuring Transactions;

                  (v)      all Liabilities relating to current or former
                           employees, officers, directors, consultants and other
                           agents of VSC or any of its current or former
                           Subsidiaries and Affiliates; and

                  (vi)     except to the extent resulting from any breach of
                           this Agreement or the VSC Merger Agreement by AT&T
                           that does not arise out of or relate to actions taken
                           by AT&T at the request of LMC (as contemplated by
                           Section 1.2(d) hereof or otherwise in writing), all
                           Liabilities arising out of the execution, delivery or
                           performance of this Agreement.

Notwithstanding the foregoing, as between the Common Stock Group and the Liberty
Media Group, the Common Stock Group shall be responsible for (i) any Liabilities
(other than any Liability arising from or relating to a VSC Tax Item (as defined
in the Eighth Tax Sharing Amendment)) to the extent arising out of or relating
to any breach by AT&T or Merger Sub E of the VSC Merger Agreement or this
Agreement, that do not arise out of or relate to actions taken or omitted to be
taken by AT&T


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or Merger Sub E at the request of LMC (as contemplated by Section 1.2(d) hereof
or otherwise in writing), whether incurred by a member of the Common Stock Group
or by a member of the Liberty Media Group, and (ii) any VSC Tax Item to the
extent set forth in Sections 3(d)(xiv) and 3(d)(xvii) of the Tax Sharing
Agreement.

                  (b) The Liberty Media Group shall be responsible for, and
shall reimburse the Common Stock Group for, any and all reasonable costs, fees
and expenses incurred by AT&T or any member of the Common Stock Group in
connection with: (i) the negotiation, review, execution and delivery of the VSC
Merger Agreement, this Agreement and the Eighth Tax Sharing Amendment; (ii) the
consummation of the transactions contemplated by the VSC Merger Agreement and
this Agreement; (iii) the preparation, review and filing of the Registration
Statement contemplated by the VSC Merger Agreement (and the Proxy Statement that
will be a part thereof); (iv) the consummation of the Post-Merger Restructuring
Transactions; (v) making any filings with any governmental entity and otherwise
assisting in obtaining approvals, consents and clearances required in connection
with the transactions contemplated by the VSC Merger Agreement and this
Agreement, if any; and (vi) all other fees and expenses related thereto,
including in each case any internal costs, fees and expenses (which shall be
determined in any reasonable manner developed by AT&T for tracking such internal
costs, fees and expenses), and in each case such costs, fees and expenses to be
reimbursed promptly upon receipt of a statement therefor.

                  (c) LMC shall indemnify and hold harmless AT&T and each member
of the Common Stock Group from and against, and pay and reimburse AT&T and each
member of the Common Stock Group for, any and all Liabilities (including
reasonable attorneys' fees and expenses)


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for which the Liberty Media Group is responsible pursuant to this Section 1.2 in
each case in accordance with Section 1.4(c) of the Inter-Group Agreement.

                  (d) Notwithstanding any provision of the VSC Merger Agreement,
AT&T and Merger Sub E shall not waive any condition to their respective
obligations to consummate the VSC Merger set forth in Article VIII of the VSC
Merger Agreement (the "Parent Closing Conditions") without LMC's prior written
consent; provided, however, that consummation of the VSC Merger by Parent based
on the reasonable belief that all of the Parent Closing Conditions applicable to
such merger have been satisfied shall not be deemed a breach of this Agreement
unless (and to the extent) AT&T receives a written request referred to in the
next sentence at least 24 hours prior to the then scheduled Closing of such
merger. To the extent so requested in writing by LMC, each of AT&T and Merger
Sub E shall (i) assert that one or more of the Parent Closing Conditions
applicable to the VSC Merger have not been satisfied and decline to consummate
the transactions contemplated by the VSC Merger Agreement, unless there is no
reasonable basis for such assertion, or (ii) to the extent lawful, waive one or
more of the Parent Closing Conditions (other than those set forth in Section 8.1
or Section 8.3(d) of the VSC Merger Agreement). The Liberty Media Group agrees
to indemnify AT&T for any Liabilities incurred by AT&T or any member of the
Common Stock Group as a result of the taking of an action by AT&T or Merger Sub
E at the request of LMC as contemplated by the previous sentence (but without
regard to whether such action constitutes a breach of the VSC Merger Agreement).
Notwithstanding clause (ii) of the second sentence of this paragraph, AT&T shall
not be obligated to waive any Parent Closing Condition and consummate the VSC
Merger if AT&T, in its reasonable judgment, determines that the foregoing
agreement of LMC to indemnify AT&T from and against any Liability incurred as a
result of such action is not


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adequate to fully protect AT&T and the Common Stock Group from and against any
Liability that could reasonably be expected to result from such waiver and the
consummation of the VSC Merger in connection therewith (it being understood that
no such indemnification would be adequate if such Liability relates to, without
limitation, any injunction applicable to AT&T or any of its Subsidiaries, any
restriction on the operation of any business or assets of AT&T or any of its
Subsidiaries or the relationship of AT&T or any of its Subsidiaries with any
governmental entity that has jurisdiction over AT&T or such Subsidiary or any of
their assets or businesses). Except as set forth in this paragraph, nothing
herein shall prohibit AT&T or Merger Sub E from exercising any of its rights
under the VSC Merger Agreement. AT&T shall reasonably consider any amendments
to, or any waiver of any other provision of, the VSC Merger Agreement proposed
by LMC. If so requested by AT&T, in connection with the closing of the VSC
Merger, LMC shall acknowledge in writing to AT&T that the consummation of such
merger would not be inconsistent with AT&T's obligations under this paragraph,
and the failure of AT&T to consummate such merger in the absence of such
acknowledgment shall be deemed, for all purposes of this Agreement, not to be a
violation of this Agreement or the VSC Merger Agreement. Upon written notice
from LMC, AT&T will consent to the repayment by VSC of certain convertible
subordinated notes made by VSC as contemplated by the letter agreement, of even
date herewith, between LMC and VSC.

                  (e) All employees, officers, directors, consultants and other
agents of VSC and its Subsidiaries shall be deemed to be employees, officers,
directors, consultants and other agents of the Liberty Media Group and all
Carryover Options that are created as a result of the VSC Merger shall be the
responsibility of the Liberty Media Group.


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                  (f) For purposes of Section 1.16 of the Inter-Group Agreement,
the Carryover Options, the obligation to issue Class A Liberty Group Stock to
shareholders of VSC pursuant to the VSC Merger Agreement, and any other
obligation to issue or sell any Class A Liberty Group Stock pursuant to or in
connection with the VSC Merger, the VSC Merger Agreement, and any agreement
referred to in the VSC Merger Agreement or executed in connection therewith (the
"VSC Issuance Obligations") shall be deemed to be Tracking Stock Obligations (as
defined in the Inter-Group Agreement) incurred with a Liberty Approval (as
defined in the Inter-Group Agreement), and the incurrence of such obligations
shall not constitute a breach of the second sentence of Section 1.16 of the
Inter-Group Agreement. The issuance of Class A Liberty Group Stock pursuant to
the VSC Merger and any other transaction contemplated by the VSC Merger
Agreement shall be deemed to have occurred with a Liberty Approval for purposes
of Section 1.11(a) of the Inter-Group Agreement and shall not be a breach of
Section 1.11(b) or (c) of the Inter-Group Agreement. Subject to the requirements
set forth in Section 1.16 of the Inter-Group Agreement that apply following a
Tax Law Change, any action taken by AT&T to implement the terms of this
paragraph (f) or otherwise to satisfy the VSC Issuance Obligations shall not
constitute a breach of any provision of the Inter-Group Agreement.

                  (g) Subject to Section 3.4(c) of the VSC Merger Agreement, at
all times from the date of its formation until the Effective Time of the VSC
Merger, Merger Sub E shall be a direct, wholly owned Subsidiary of AT&T.

                  SECTION 1.3. Allocation of Proceeds. For purposes of Sections
1.6(b) and 1.11 of the Inter-Group Agreement and the definition of the term
"Liberty Media Group" in the AT&T Charter Amendment, the net proceeds of the
issuance of the Class A Liberty Group Stock


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to be issued in the VSC Merger shall consist of the entire interest of AT&T in
VSC and each of its respective Subsidiaries other than any interest in AT&T
Liberty Tracking Shares (the "Excluded Shares") received in respect of any
shares of common stock of VSC owned by AT&T or any of its Subsidiaries
immediately prior to the Effective Time. Following the Effective Time, the
Surviving Entity and its Subsidiaries shall be members of the Liberty Media
Group. For purposes of Section 1.6(b) of the Inter-Group Agreement, all proceeds
received by VSC upon exercise or conversion of any options, warrants, debentures
or other securities that may be exercised, converted or exchanged in whole or in
part for shares of Class A Liberty Group Stock shall be deemed to have been
received by or contributed to LMC, without any further action by Parent or any
other Person. Notwithstanding anything to the contrary in the Inter-Group
Agreement, there shall be no restriction on the Transfer of any Excluded Shares
and there shall be no obligation to contribute to LMC the net proceeds from any
such Transfer(s).

                  In furtherance of the foregoing, any contract right or other
similar right associated with any asset that is attributed to a Group (as
defined in the Inter-Group Agreement) in accordance with the preceding paragraph
shall be the right of the Group (as defined in the Inter-Group Agreement) to
which such related asset is so attributed.

                  SECTION 1.4. Certain Obligations.

                  (a) AT&T agrees to reasonably consider any actions that it may
be requested by LMC to take in accordance with consummation of the VSC Merger.

                  (b) LMC represents and warrants that true and complete copies
of all documents referred to in the VSC Merger Agreement that have been
delivered to LMC by or on behalf of VSC on or prior to the date hereof have been
delivered to AT&T on or prior to the date hereof and agrees


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that true and complete copies of all such documents delivered to LMC from and
after the date hereof until consummation of the transactions contemplated hereby
will be delivered promptly to AT&T.

                  (c) To the fullest extent possible, LMC will perform all
obligations of AT&T under Sections 3.2 and 3.4 of the VSC Merger Agreement, such
as (to the extent, if any, required of Parent thereby) preparation of documents
and filings, and seeking necessary consents. In connection with the foregoing,
LMC will not make any filing or take any action in the name of or on behalf of
AT&T without receiving the prior written consent of AT&T.

                  (d) AT&T acknowledges that its covenants in this Agreement and
the VSC Merger Agreement are subject to the fiduciary duties of its board of
directors to all of its stockholders, including the holders of Parent Common
Stock and the holders of AT&T Liberty Tracking Shares, in each case in
accordance with the Parent Charter and the AT&T board of directors' Policy
Statement regarding Liberty Media Group Tracking Stock Matters.

                                   ARTICLE II
                                   DEFINITIONS

                  SECTION 2.1. Certain Definitional Provisions. Capitalized
terms used herein without definition have the meanings ascribed to such terms in
(i) the VSC Merger Agreement or (ii) if not otherwise defined herein or in the
VSC Merger Agreement, the Inter-Group Agreement. The language used in this
Agreement shall be deemed to be the language chosen by the parties to express
their mutual intent, and no rule of strict construction shall be applied against
any party. Any references to any statute or law shall also refer to all rules
and regulations promulgated thereunder, unless the context requires otherwise.
Whenever the context may require, any pronoun shall include the corresponding
masculine, feminine and neuter forms. The words "include," "includes," and


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"including" shall be deemed to be followed by the phrase "without limitation."
The words "hereof," "herein" and "hereunder" and words of similar import when
used in this Agreement shall refer to this Agreement as a whole and not to any
particular provision of this Agreement, and Article and Section references are
to this Agreement unless otherwise specified. The meanings given to terms
defined herein shall be equally applicable to both the singular and plural forms
of such terms. Unless the context shall otherwise require, any references to any
agreement or other instrument or statute or regulation are to it as amended and
supplemented from time to time (and, in the case of a statute or regulation, to
any successor provisions). Any reference in this Agreement to a "day" or number
of "days" (without the explicit qualification of "business") shall be
interpreted as a reference to a calendar day or number of calendar days. If any
action or notice is to be taken or given on or by a particular calendar day, and
such calendar day is not a business day, then such action or notice shall be
deferred until, or may be taken or given on, the next business day.

                                   ARTICLE III
                                  MISCELLANEOUS

                  SECTION 3.1. Notices. All notices, requests, demands or other
communications required by or otherwise with respect to this Agreement shall be
in writing and shall be deemed to have been given to any party when delivered
personally (by courier service or otherwise), when delivered by telecopy and
confirmed by return telecopy, or upon the receipt after being mailed by
first-class mail, postage prepaid and return receipt requested in each case to
the applicable addresses set forth below:


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         If to AT&T or any member of the Common Stock Group:

                  AT&T Corp.
                  295 North Maple Avenue
                  Basking Ridge, New Jersey  07920
                  Attention:   Vice President-Law
                               and Corporate Secretary
                  Facsimile:   (908) 221-6618

         with a copy to:

                  Wachtell, Lipton, Rosen & Katz
                  51 West 52nd Street
                  New York, New York 10019
                  Attention:   Richard D. Katcher, Esq.
                               Steven A. Rosenblum, Esq.
                               David M. Silk, Esq.
                  Facsimile:   (212) 403-2000

         If to LMC or any member of the Liberty Media Group:

                  Liberty Media Corporation
                  9197 South Peoria Street
                  Englewood, Colorado 80112
                  Attention:   Charles Y. Tanabe, Esq.
                  Facsimile:   (720) 875-5382

         with a copy to:

                  Baker Botts L.L.P.
                  599 Lexington Avenue
                  New York, New York 10022
                  Attention:   Elizabeth M. Markowski, Esq.
                               Marc A. Leaf, Esq.
                  Facsimile:   (212) 705-5125

or such address as such party shall have designated by notice so given to each
other party.

                  SECTION 3.2. Amendments; No Waivers. (a) This Agreement shall
be amended, changed, supplemented, waived or otherwise modified only by an
instrument in writing



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signed by each of AT&T and LMC (and following a Triggering Event (as defined in
the Inter-Group Agreement), Liberty Media Group LLC).

                  (b) No failure or delay by any party in exercising any right,
power or privilege hereunder shall operate as a waiver thereof nor shall any
single or partial exercise thereof preclude any other or further exercise
thereof or the exercise of any other right, power or privilege. The rights and
remedies herein provided shall be cumulative and not exclusive of any rights or
remedies provided by law.

                  SECTION 3.3. Successors and Assigns. Neither this Agreement
nor any of the rights or obligations under this Agreement shall be assigned, in
whole or in part, by any party without the prior written consent of the other
parties hereto; provided, however, that the assignment of its rights and
obligations under this Agreement by LMC or any Covered Entity (as defined in the
Inter-Group Agreement) to Liberty Media Group LLC in connection with the
transactions contemplated by the Contribution Agreement shall not require the
consent of AT&T. Subject to the foregoing, the provisions of this Agreement
shall be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns.

                  SECTION 3.4. Governing Law; Consent to Jurisdiction. This
Agreement and all disputes hereunder shall be governed by and construed and
enforced in accordance with the internal laws of the State of Delaware, without
regard to the principles of conflicts of laws. Each party hereto irrevocably and
unconditionally consents to submit to the exclusive jurisdiction of the United
States District Court for the District of Delaware or the Chancery Court of the
State of Delaware in any action, suit or proceeding arising in connection with
this Agreement, and agrees that any such action, suit or proceeding shall be
brought only in such court (and waives any objection


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based on forum non coveniens or any other objection to venue therein); provided,
however, that such consent to jurisdiction is solely for the purpose referred to
in this Section 3.4 and shall not be deemed to be a general submission to the
jurisdiction of said courts or of the State of Delaware other than for such
purpose. AT&T and LMC each hereby waive any right to a trial by jury in
connection with any such action, suit or proceeding.

                  SECTION 3.5. Counterparts; Effectiveness. This Agreement may
be executed in any number of counterparts, each of which shall be deemed to be
an original, but all of which together shall constitute one instrument. This
Agreement shall become effective when each party hereto shall have received
counterparts thereof signed by each other party hereto.

                  SECTION 3.6. Specific Performance. Each of AT&T and LMC
acknowledges and agrees that money damages are not an effective remedy for
violations of this Agreement and that any party may, in its sole discretion,
apply to a court of competent jurisdiction for specific performance or
injunctive or such other relief as such court may deem just and proper in order
to enforce this Agreement or prevent any violation hereof and, to the extent
permitted by applicable Law, each party waives any objection to the imposition
of such relief.

                  SECTION 3.7. Remedies Cumulative. All rights, powers and
remedies provided under this Agreement or otherwise available in respect hereof
at law or in equity shall be cumulative and not alternative, and the exercise or
beginning of the exercise of any thereof by any party shall not preclude the
simultaneous or later exercise of any other such right, power or remedy by such
party.

                  SECTION 3.8. Termination. This Agreement shall remain in full
force and effect until the earlier to occur of (i) such time as no Class A
Liberty Group Stock or Class B Liberty


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Group Stock are outstanding and (ii) the termination prior to the Effective Time
of the VSC Merger Agreement, at which time this Agreement shall terminate and
upon termination, no party shall have any liability or further obligation to the
other under this Agreement, except that the provisions of Section 1.2(a) (other
than subsections 1.2 (a) (i) and (v), Section 1.2 (b), Section 1.2(c) (to the
extent of any Liabilities described therein that arose at or prior to the
termination of this Agreement or under any provision of this Agreement that
survives such termination) and this Section 3.8 shall survive the termination of
this Agreement; provided, however, that such termination shall not relieve any
party hereto of any liability for any breach of this Agreement or the VSC Merger
Agreement. No termination of this Agreement shall limit or otherwise affect the
rights or obligations of the parties to the Inter-Group Agreement.

                  SECTION 3.9. Severability. In case any provision in this
Agreement shall be held invalid, illegal or unenforceable in a jurisdiction,
such provision shall be modified or deleted, as to the jurisdiction involved,
only to the extent necessary to render the same valid, legal and enforceable,
and the validity, legality and enforceability of the remaining provisions hereof
shall not in any way be affected or impaired thereby nor shall the validity,
legality or enforceability of such provision be affected thereby in any other
jurisdiction.

                  SECTION 3.10. Cooperation. Each of AT&T and LMC covenants and
agrees with the other to use its reasonable best efforts to cause each member of
the Common Stock Group and each member of the Liberty Media Group, respectively,
to fulfill each of its respective obligations under this Agreement.


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                  IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be duly executed as of the day and year first above written.

                                    AT&T CORP.



                                    By: /s/
                                        ----------------------------------------
                                        Name:
                                        Title:

                                    LIBERTY MEDIA CORPORATION



                                    By: /s/
                                        ----------------------------------------
                                        Name:
                                        Title:

                                    LIBERTY MEDIA GROUP LLC



                                    By: /s/
                                        ----------------------------------------
                                        Name:
                                        Title:




<PAGE>   20



                                    Each of the following Covered Entities
                                    hereby executes this Agreement as a member
                                    of the Liberty Media Group to become a party
                                    to this Agreement for so long as it remains
                                    a Covered Entity under the applicable
                                    provisions of the AT&T Charter Amendment:


                                    LIBERTY SP, INC.



                                    By: /s/
                                        ----------------------------------------
                                        Name:
                                        Title:

                                    LIBERTY AGI, INC.



                                    By: /s/
                                        ----------------------------------------
                                        Name:
                                        Title:

                                    LMC INTERACTIVE, INC.



                                    By: /s/
                                        ----------------------------------------
                                        Name:
                                        Title:



<PAGE>   21



                                    EXHIBIT A

                 UNANIMOUS WRITTEN CONSENT IN LIEU OF MEETING OF
                         THE CAPITAL STOCK COMMITTEE OF
                      THE BOARD OF DIRECTORS OF AT&T CORP.


                  Pursuant to Article V of the By-laws of AT&T Corp., a New York
corporation (the "Company"), and Section 708 of the New York Business
Corporation Law, the undersigned, being all the members of the Capital Stock
Committee of the Board of Directors of AT&T Corp. (this "Capital Stock
Committee"), hereby by unanimous written consent approve the following
resolution:

                  RESOLVED, that the form, terms and provisions of the Agreement
and Plan of Merger (the "VSC Merger Agreement") among the Company, E-Group
Merger Corp., a wholly owned subsidiary of the Company, Liberty Media
Corporation and Video Services Corporation and the transactions contemplated
thereby are hereby approved and adopted in all respects in substantially the
form described to this Capital Stock Committee, with such changes therein as the
officers of the Company executing the same shall approve;

                  RESOLVED, that the form, terms and provisions of the Seventh
Supplement to Inter-Group Agreement (the "Inter-Group Supplement") between and
among the Company, on the one hand, and Liberty Media Corporation, Liberty Media
Group LLC and each Covered Entity listed on the signature pages thereof, on the
other hand, and the transactions contemplated thereby are hereby approved and
adopted in all respects in substantially the form described to this Capital
Stock Committee, with such changes therein as the officers of the Company
executing the same shall approve;


<PAGE>   22



                  RESOLVED, that the form, terms and provisions of the Eighth
Amendment to Tax Sharing Agreement (the "Tax Sharing Amendment") by and among
the Company, Liberty Media Corporation, Tele-Communications, Inc., Liberty
Ventures Group LLC, Liberty Media Group LLC, TCI Starz, Inc., TCI CT Holding,
Inc. and each Covered Entity listed on the signature pages thereof and the
transactions contemplated thereby are hereby approved and adopted in all
respects, in each case in substantially the form described to this Capital Stock
Committee, with such changes therein as the officers of the Company executing
the same shall approve;

                  RESOLVED, that the Inter-Group Supplement is in the best
interests of the Company and all of its shareholders after giving fair
consideration to the potentially divergent interests and all other relevant
interests of the holders of the separate classes of common stock of the Company,
and that the matters and allocations contemplated by Section 1.3 of the Inter-
Group Supplement are hereby specifically approved and ratified;

                  RESOLVED, that the foregoing resolutions of this Committee be
communicated to the Board of Directors of the Company, together with a
recommendation of this Capital Stock Committee that the Board of Directors of
the Company approve the VSC Merger Agreement, the Inter-Group Supplement and the
Tax Sharing Amendment, and the transactions contemplated thereby;

                  RESOLVED, that the proper officers of the Company be, and each
of them hereby is, authorized, empowered and directed, in the name and on behalf
of the Company, to execute and deliver or cause to be executed and delivered any
or all instruments, agreements or documents, and to do or cause to be done any
and all such other acts or things as, in the opinion


                                        2
<PAGE>   23



of any such officer, may be necessary, appropriate or desirable in order to
enable the Company fully and promptly to carry out the intent and purpose of the
foregoing and consummate the proposed transaction, and any such action taken or
any agreement, instrument or document executed and delivered by them in
connection with any such action shall be conclusive evidence of such officers'
authority to take, execute and deliver the same, and to pay any and all expenses
and fees arising in connection with any of the foregoing; and

                  RESOLVED, that actions heretofore taken by any of the
officers, directors, employees, representatives or agents of the Company on
behalf of the Company in connection with the matters contemplated by the
foregoing are hereby ratified, confirmed and approved as acts and deed of the
Company.


                                        3
<PAGE>   24




Dated: __________ ___, 2000



                                                   ----------------------------
                                                   Donald V. Fites



                                                   ----------------------------
                                                   John C. Malone



                                                   ----------------------------
                                                   Michael I. Sovern


                                        4