FORM OF PROXY

American Century Mutual Funds

         THIS PROXY IS SOLICITED  BY THE BOARD OF DIRECTORS OF American  Century
Mutual Funds, Inc. for use at a meeting of shareholders to be held at 10:00 a.m.
(Central time) on August 8, 1998 at American  Century Tower I, 4500 Main Street,
Kansas City, Missouri.

         I hereby appoint Patrick A. Looby and Charles A. Etherington,  and each
of them,  with full power of substitution as my proxy to vote at the meeting and
at all adjournments or postponements thereof, all shares of beneficial interest,
evidencing  interests in the American  Century - Benham Cash Reserve Fund ("Cash
Reserve")  which I held of  record  on May 15,  1998,  the  record  date for the
meeting,  upon the  following  matters and upon any other  matter which may come
before the meeting, in their discretion:

               1.   Proposal to approve an Agreement and Plan of  Reorganization
                    and the transactions  contemplated thereby,  including:  the
                    transfer of substantially  all of the assets and liabilities
                    of Cash Reserve to the American Century - Benham Prime Money
                    Market Fund ("Prime");  the  distribution of Prime shares to
                    the   shareholders  of  Cash  Reserve   according  to  their
                    respective  interests;  and the termination  under state law
                    and the Investment Company Act of 1940, as amended,  of Cash
                    Reserve.

                           FOR          AGAINST        ABSTAIN
                          /  /           /  /           /  /

               2.   In their discretion, the parties are authorized to vote upon
                    such other business as may properly come before the meeting.

                           FOR          AGAINST        ABSTAIN
                          /  /           /  /           /  /


         Every  properly  signed  proxy  will be voted in the  manner  specified
hereon  and,  in the  absence of  specification,  will be  treated  as  GRANTING
authority to vote FOR Proposals 1 and 2.

         PLEASE SIGN, DATE AND RETURN THE PROXY CARD PROMPTLY USING THE ENCLOSED
ENVELOPE.

         Please sign  exactly as name  appears  hereon.  When shares are held by
joint  tenants,  both should  sign.  When  signing as  attorney or as  executor,
administrator,  trustee  or  guardian,  please  give  full  title as such.  If a
corporation, please sign in full corporate name by president or other authorized
officer. If a partnership, please sign in partnership name by authorized person.

Dated:  _____________________________________________
X____________________________________________________
Signature
X____________________________________________________
Signature, if held jointly

Please execute and return  promptly in the enclosed  envelope each  accompanying
proxy card which is being  solicited by your Board of  Directors.  Please return
your  proxy  card  even if you are  planning  to  attend  the  meeting.  This is
important to ensure a quorum at the meeting.  Proxies may be revoked at any time
before they are exercised by  submitting to a written  notice of revocation or a
subsequently executed proxy or by attending the meeting and voting in person.