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                                                                 Exhibit 10.4


                                    AMENDMENT NO. 1 (this "Amendment") dated as
                           of April 17 2000, to the AMENDED AND RESTATED CREDIT
                           AGREEMENT (the "Agreement") entered into as of
                           December 10, 1999, among INFINITY BROADCASTING
                           CORPORATION, a Delaware corporation ("Infinity");
                           each Subsidiary Borrower (as defined in the
                           Agreement); CBS CORPORATION, a Pennsylvania
                           corporation ("CBS"), as a guarantor; the Lenders (as
                           defined in the Agreement); BANK OF AMERICA, N.A.
                           ("Bank of America") and THE TORONTO-DOMINION BANK
                           ("Toronto Dominion"), as syndication agents for the
                           Lenders (in such capacity, the "Syndication Agents");
                           THE CHASE MANHATTAN BANK, a New York banking
                           corporation ("Chase"), as documentation agent for the
                           Lenders; and MORGAN GUARANTY TRUST COMPANY OF NEW
                           YORK, a New York banking corporation ("Morgan"), as
                           administrative agent for the Lenders.

                  The Agreement is hereby amended as follows:

                  SECTION 1. Amendment. (a) The definition of the term "CBS
Consolidated EBITDA" is hereby deleted and replaced in its entirety by the
following new definition:

                  "CBS Consolidated EBITDA" shall mean, with respect to CBS and
                  its Consolidated Subsidiaries for any period, operating profit
                  (loss) (excluding that related to Discontinued Operations),
                  plus other income (loss), plus interest income, plus
                  depreciation and amortization (excluding amortization related
                  to programming rights, prepublication costs and
                  videocassettes), excluding (a) gains (losses) on sales of
                  assets (except (I) gains (losses) on sales of inventory sold
                  in the ordinary course of business and (II) gains (losses) on
                  sales of other assets if such gains (losses) are less than
                  $10,000,000 individually and less than $50,000,000 in the
                  aggregate during such period), (b) other non-cash items
                  (including (i) provisions for losses and additions to
                  valuation allowances, (ii) provisions for restructuring,
                  litigation and environmental reserves and losses on the
                  Disposition of businesses and (iii) pension settlement
                  charges), in each case determined for such period on a basis
                  consistent with that reported in CBS's Form 10-Q for the
                  fiscal quarter ended September 30, 1998 filed with the SEC,
                  minus cash payments made



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                  during such period in respect of non-cash charges taken during
                  any previous period (excluding cash payments in respect of
                  non-cash charges taken prior to December 31, 1998) and (c)
                  nonrecurring expenses incurred in connection with the merger
                  of CBS and Viacom Inc. ("Viacom") pursuant to the Agreement
                  and Plan of Merger dated as of September 6, 1999, as amended
                  and restated as of October 8, 1999 and as of November 23,
                  1999, by and among CBS, Viacom and Viacom/CBS LLC.

                  (b) The definition of the term "CBS Consolidated Total Funded
Indebtedness" in Section 1.1 of the Agreement is hereby deleted and replaced in
its entirety by the following new definition:

                  "CBS Consolidated Total Funded Indebtedness" shall mean with
                  respect to CBS and its Consolidated Subsidiaries at any date,
                  without duplication, (i) all obligations of such Person for
                  borrowed money (including, without limitation, in the case of
                  the Borrower, the obligations of the Borrower for borrowed
                  money under this Agreement), (ii) all obligations of such
                  Person evidenced by bonds, debentures, notes or other similar
                  instruments, (iii) all obligations of such Person to pay the
                  deferred purchase price of Property or services, except as
                  provided below, (iv) all obligations of such Person as lessee
                  under Capital Lease Obligations, (v) all Indebtedness of
                  others secured by a Lien on any Property of such Person,
                  whether or not such Indebtedness is assumed by such Person,
                  (vi) all Indebtedness of others directly or indirectly
                  guaranteed or otherwise assumed by such Person, including any
                  obligations of others endorsed (otherwise than for collection
                  or deposit in the ordinary course of business) or discounted
                  or sold with recourse by such Person, or in respect of which
                  such Person is otherwise directly or indirectly liable,
                  including, without limitation, any Indebtedness in effect
                  guaranteed by such Person through any agreement (contingent or
                  otherwise) to purchase, repurchase or otherwise acquire such
                  obligation or any security therefor, or to provide funds for
                  the payment or discharge of such obligation, or to maintain
                  the solvency or any balance sheet or other financial condition
                  of the obligor of such obligation, provided that Indebtedness
                  of the Borrower and its Subsidiaries shall not include
                  guarantees of Indebtedness that


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                  are identified on Schedule 1.1 hereto, (vii) all obligations
                  of such Person as issuer, customer or account party under
                  letters of credit or bankers' acceptances that are either
                  drawn or that back financial obligations that would otherwise
                  be Indebtedness; provided, however, that in each of the
                  foregoing clauses (i) through (vii) Indebtedness shall not
                  include (a) obligations of CBS and its Subsidiaries in
                  connection with Discontinued Operations and (b) obligations
                  (other than under the Existing Credit Agreement, as amended
                  and restated, or the Amended and Restated Viacom International
                  Inc. Credit Agreement, dated as of March 26, 1997, among
                  Viacom International Inc., the banks parties thereto, The Bank
                  of New York, Citibank, N.A., Morgan Guaranty Trust Company of
                  New York, Bank of America NT&SA and The Chase Manhattan Bank,
                  as Managing Agents, The Bank of New York, as Documentation
                  Agent, Citibank, N.A., as the Administrative Agent, JP Morgan
                  Securities Inc. and Bank of America NT&SA, as the Syndication
                  Agents, the banks identified as Agents on the signature pages
                  thereof, as Agents, and the banks identified as Co-agents on
                  the signature pages thereof, as Co-Agents) specifically with
                  respect to the production, distribution and acquisition of
                  motion pictures or other programming rights, talent or
                  publishing rights.

                  (c) Section 1.1 of the Agreement is hereby amended by
inserting the following definition for the term "New Infinity Credit Agreements"
in the appropriate alphabetical order:

                  "New Infinity Credit Agreements" shall mean the 364-Day Credit
                  Agreement and the Five-Year Credit Agreement among Infinity,
                  the Subsidiary Borrowers (as defined therein) parties thereto,
                  the lenders named therein, Bank of America, N.A. and
                  FleetBoston, as syndication agents, The Bank of New York, as
                  documentation agent and The Chase Manhattan Bank as
                  administrative agent, as amended, supplemented or otherwise
                  modified from time to time.

                  (d) Section 5.6 of the Agreement is hereby amended:

                  (i) by inserting the words "and the New Infinity Credit
         Agreements" before the word "and" in clause (ii) thereof; and


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                  (ii) by substituting "$600,000,000" for "$300,000,000" at the
         end thereof.

                  (e) Section 5.7 of the Agreement is hereby amended by
inserting a comma followed by the following words immediately preceding the
colon therein:

                  provided that as soon as and for so long as the senior
                  unsecured long-term debt ratings of Infinity are equal to or
                  greater than A- by S&P and A3 by Moody's for any period, such
                  condition shall be suspended.


                  (f) Section 5.8 of the Agreement is hereby amended by
inserting a comma immediately followed by the following words at the end
thereof:

                  provided that as soon as and for so long as the senior
                  unsecured long-term debt ratings of Infinity are equal to or
                  greater than A- by S&P and A3 by Moody's for any period, such
                  condition shall be suspended.

                  (g) Section 5.11 of the Agreement is hereby deleted in its
entirety.

                  SECTION 2. Conditions to Effectiveness. This Amendment shall
become effective as of the date of the consummation of the merger of CBS and
Viacom pursuant to the Agreement and Plan of Merger dated as of September 6,
1999, as amended and restated as of October 8, 1999 and as of November 23, 1999,
by and among CBS Corporation, Viacom Inc. and Viacom/CBS LLC; provided that
Sections 1(d) and 1(g) of this Amendment, shall become effective as of the date
on which the Administrative Agent shall have received counterparts of this
Amendment that, when taken together, bear the signatures of the Borrower and the
Required Lenders under the Agreement.

                  Except as expressly set forth above, all the provisions of the
Agreement are hereby ratified and confirmed by all the parties and shall remain
in full force and effect. All references in the Agreement to "this Agreement"
shall be read as references to the Agreement, as amended by this Amendment.

                  SECTION 3. Counterparts. This Amendment may be executed in two
or more counterparts, all of which shall be considered one and the same
agreement.


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                  SECTION 4. Applicable Law. This Amendment shall be construed
in accordance with and governed by the laws of the State of New York applicable
to agreements made within such State, without regard to conflicts of law
provisions and principles of such State.


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


                                  INFINITY BROADCASTING CORPORATION,

                                    by /s/ Farid Suleman
                                       ----------------------------------
                                      Name:   Farid Suleman
                                      Title:  Executive Vice President,
                                              Chief Financial Officer
                                              and Treasurer


                                  MORGAN GUARANTY TRUST COMPANY OF
                                  NEW YORK, as Administrative Agent,

                                    by /s/ Dennis Wilczek
                                       ---------------------------------
                                       Name:  Dennis Wilczek
                                       Title: Associate


                                  CBS CORPORATION, as guarantor,

                                    by /s/ Farid Suleman
                                       ---------------------------------
                                       Farid Suleman
                                       Sr. Vice President, Finance
                                       and Treasurer