<PAGE>




                                        Charles River Associates Incorporated
                                        John Hancock Tower
                                        Boston, Massachusetts

                          FIFTEENTH AMENDMENT OF LEASE

     THIS FIFTEENTH AMENDMENT OF LEASE, made and entered into as of this 7th day
of June, 2002, by and between JOHN HANCOCK LIFE INSURANCE COMPANY, formerly
known as John Hancock Mutual Life Insurance Company (hereinafter referred to as
"Landlord") and CHARLES RIVER ASSOCIATES INCORPORATED (hereinafter referred to
as "Tenant").

                               WITNESSETH:  THAT

     WHEREAS, Landlord and Tenant entered into a lease dated March 1, 1978,
demising certain premises in the John Hancock Tower, 200 Clarendon Street,
Boston, Massachusetts (the "Building"), which lease has been amended by First
Amendment of Lease dated December 16, 1981, Second Amendment of Lease dated
February 24, 1984, Third Amendment of Lease dated February 28, 1985, Fourth
Amendment of Lease dated February 7, 1986, Fifth Amendment of Lease dated
February 13, 1987, Sixth Amendment of Lease dated August 24, 1987, Seventh
Amendment of Lease dated January 31, 1990, Eighth Amendment of Lease dated
December 31 1991, Ninth Amendment of Lease dated September 2, 1992 (the "Ninth
Amendment"), Tenth Amendment of Lease dated August 24, 1995, Eleventh Amendment
to Lease dated November 25, 1996, Twelfth Amendment of Lease dated March 19,
1998, Thirteenth Amendment to Lease dated August 13, 1999 and Fourteenth
Amendment to Lease dated April 20, 2000 (which lease and the amendments thereto
are hereinafter collectively referred to as the "Lease"); and

     WHEREAS, Tenant wishes to lease certain additional space located on the
31st floor of the Building; and

     WHEREAS, Landlord and Tenant wish to make certain revisions to the Lease
to reflect the remeasurement of the Building; and

     WHEREAS, the parties hereto are mutually desirous of amending the Lease so
as to provide for the above.

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                                      -2-



      NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the Lease is hereby amended as
follows:

     1.   Definitions. Defined terms in this Fifteenth Amendment of Lease shall
          have the same meaning as provided for in the Lease.

Remeasurement of Building

     2.   Remeasurement of Building. At the time of execution of the Lease, the
          number of square feet of rentable area in the Building was 1,597,533
          square feet calculated using Landlord's original building measurement
          standard ("Original Standard"). The resultant number of square feet of
          rentable area in the Premises and Tenant's Proportionate Share were
          similarly calculated using the Original Standard. Effective as of
          January 1,2000, Landlord remeasured the Building using a modified BOMA
          standard ("Modified BOMA Standard"). Pursuant to the Modified BOMA
          Standard the number of square feet of rentable area in the Building is
          1,738,779 square feet. Landlord and Tenant hereby confirm and
          acknowledge that effective October 1, 2001 all references in the Lease
          to the number of square feet of rentable area in the Building, the
          Premises, the Expansion Premises, the T-31 Premises (as defined in
          Section 5 below), the Additional Expansion Premises (as defined in
          Section 10 below), and Tenant's Proportionate Share shall be
          calculated using the Modified BOMA Standard, as more specifically
          indicated below:

          -    rentable area included in the Building:  1,738,779 square feet

          -    rentable area in the Premises:

          <Table>
                         <S>                           <C>
                         T-32                          28,803 square feet (as
                                                       outlined on Exhibit A-1
                                                       attached hereto and
                                                       incorporated by reference,
                                                       herein the "T-32 Premises")

                         T-33                          28,492 square feet (as
                                                       outlined on Exhibit A-2
                                                       attached hereto and
                                                       incorporated by reference,
                                                       herein the "T-33 Premises")

                         Total                         57,295 square feet


          </Table>

<PAGE>
                                      -3-


     -  Tenant's Proportionate Share of              3.295% (i.e., 57,295 square
        Ownership Taxes:                             feet of rentable area
                                                     included in the Premises
                                                     divided by 1,738,779, the
                                                     number of square feet of
                                                     rentable area included in
                                                     the Building)

     -  T-31 Premises:                               6,000 square feet

     -  Additional Expansion Premises:               22,090 square feet

3.   Adjustment to Base Rent re: Remeasurement.  As a result of the
     remeasurement of the Building the Base Rent must be adjusted to provide
     for the same effective Base Rent as is currently provided under the
     Lease.  As a result, effective October 1, 2001 and continuing for the
     balance of the Extended Term (i.e., April 25, 2008) Base Rent for the
     Premises (other than the T-31 Premises referenced herein, which Base Rent
     shall be payable in such amounts as provided in Section 6 of this
     Fifteenth Amendment) shall be payable by Tenant to Landlord as follows:

          With respect to T-32:

            -  For the period from                  $956,637.95 per year (28,803
               October 1, 2001 through              rentable square feet at
               August 31, 2003:                     $33.2131 per square foot),
                                                    payable in equal monthly
                                                    installments of $79,719.83

            -  For the period from                  $990,917.70 per year (28,803
               September 1, 2003                    rentable square feet at
               through February 28,                 $34.4033 per square foot),
               2004:                                payable in equal monthly
                                                    installments of $82,576.48

            -  For the period from                  $991,916.70 per year (28,803
               March 1, 2004 through                rentable square feet at
               April 25, 2008:                      $34.4380 per square foot),
                                                    payable in equal monthly
                                                    installments of $82,659.73


          With respect to T-33:

            -  For the period from                  $713,322.50 per year (28,492




<PAGE>
                                        -4-

               October 1, 2001 through     rentable square feet at
               April 25, 2008:             $25.0359 per square foot
                                           payable in equal monthly
                                           installments of $59,443.54

     4.  Adjustment to Base Rent during Option Term re:  Remeasurement.  As a
         result of the remeasurement of the Building the Base Rent during the
         Option Term must be adjusted to provide for the same effective Base
         Rent as is currently provided under the Lease. As a result Section 9
         of the Ninth Amendment is hereby amended as follows:

         (i)  By deleting in its entirety the first paragraph on page 18 of the
              Ninth Amendment which currently reads:

                "Base Rent during the Option Term shall be equal to the Fair
                Rental Value for the Extended Premises (as defined and
                determined below)."

              and by inserting the following in its stead:

                "Base Rent during the Option Term shall be equal to ninety-two
                (92%) percent of the Fair Rental Value for the T-32 Premises and
                T-33 Premises, and equal to one hundred (100%) percent of the
                Fair Rental Value for the balance of the Extended Premises,
                including but not limited to the T-31 Premises and the
                Additional Expansion Premises (as defined and determined
                below)."

         (ii) By deleting in its entirety subclause (c) on page 18 of the Ninth
              Amendment which currently reads:

                "(c) the method by which square footage in measured is similar
                to the method used to measure the Extended Premises; and"

              and by inserting the following in its stead:

                "(c) the method by which square footage is measured is similar
                to the Modified BOMA Standard; and",

T-31 Premises

     5.  T-31 Premises.  Effective August 1, 2001, the Premises shall be
         increased by including 6,000 square feet of space located on the 31st
         floor and more particularly described on Exhibit A-3 attached hereto
         (herein the "T-31 Premises").  Landlord delivered the T-31 Premises to

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                                      -5-



     Tenant on August 1, 2001, in "AS IS" condition, vacant, free and clear of
     all leases and occupancies.

6.   T-31 Premises Base Rent.  Providing Tenant is not in default beyond any
     applicable grace period, Tenant shall not be obligated to pay Base Rent for
     the T-31 Premises during the months of August, September and October of
     2001.  Effective November 1, 2001 and continuing through September 30, 2004
     the Base Rent for the T-31 Premises shall be $360,000.00 per year (6,000
     rentable square feet at $60.00 per square foot), payable by Tenant to
     Landlord in equal monthly installments of $30,000.00.  Effective October 1,
     2004 and continuing through April 25, 2008 (i.e. the expiration of the
     Extended Term) the Base Rent for the T-31 Premises shall be $372,000.00
     (6,000 rentable square feet at $62.00 per square foot), payable by Tenant
     to Landlord in equal monthly installments of $31,000.00. Tenant's
     Proportionate Share of Ownership Taxes, Operating Expenses and Utility
     Expenses with respect to the T-31 Premises shall be as set forth in Section
     7 herein.

7.   T-31 Premises - Operating Expenses/Ownership Taxes.  The Base Year for
     purposes of calculating Tenant's rent adjustment for Operating Expenses for
     the T-31 Premises shall be calendar year 2001, such that Tenant shall
     commence payment of Tenant's rent adjustment for Operating Expenses for the
     T-31 Premises from and after January 1, 2002.  The Base Year for purposes
     of calculating Tenant's Proportionate Share of Ownership Taxes for the T-31
     Premises shall be the fiscal year 2002, such that Tenant shall commence
     payment of Tenant's Proportionate Share of Ownership Taxes for the T-31
     Premises from and after July 1, 2002. Tenant's Proportionate Share of
     Ownership Taxes for the T-31 Premises for any fiscal year shall be 0.336%,
     the percentage resulting from dividing the number of square feet of
     rentable area included in T-31 Premises (6,000 square feet) by the number
     of square feet of rentable area in the Building (which is 1,783,779 square
     feet).

8.   T-31 Premises - Tenant Allowance.  Tenant shall be responsible to design
     and construct all improvements within the T-31 Premises, at Tenant's sole
     expense, which design and construction shall be conducted in accordance
     with the provisions of Section 10B of the Lease. Landlord will provide
     Tenant with a tenant improvement allowance for construction of
     improvements in the T-31 Premises in the aggregate amount of $198,000.00
     ($33.00 per rentable square foot) (the "T-31 Premises Tenant Allowance").
     During construction of the improvements in the T-31 Premises (but no more
     often than once per month), Tenant shall submit a bill or bills to
     Landlord for reimbursement of the actual costs incurred by Tenant to date
     to produce plans,
<PAGE>
                                      -6-



          construct improvements, purchase furniture, fixtures or equipment or
          pay moving expenses. Tenant shall attach to such bill or bills all
          relevant and available invoices and other evidence of the completion
          of work as Landlord may require in its reasonable discretion. Within
          fifteen (15) business days of its receipt of such bill or bills from
          Tenant, provided Tenant is not in default hereunder, Landlord shall
          reimburse Tenant for all reasonable verifiable costs incurred by
          Tenant in constructing the improvements to the T-31 Premises up to the
          maximum T-31 Premises Tenant Allowance. In the event that Tenant
          completes construction of the improvements to the T-31 Premises and
          the actual costs to complete such improvements are less than the T-31
          Premises Tenant Allowance, the Base Rent due and payable by Tenant to
          Landlord for the T-31 Premises shall be reduced on a dollar for dollar
          basis until such T-31 Premises Tenant Allowance is expended in full.

               Tenant shall pay Landlord a construction management fee equal to
          one and one half (1.5%) percent (1.5) of the total project cost of any
          improvements to the T-31 Premises, such fee to be billed on a monthly
          basis and due and payable within thirty (30) days of receipt of
          Landlord's invoice.

     9.   T-31 Premises Parking. Notwithstanding the provisions of Section 12 of
          the Ninth Amendment, in connection with Tenants's occupancy of the
          T-31 Premises Landlord shall make available one (1) parking permit per
          2,500 square feet of rentable square feet in the T-31 Premises(vs. one
          per 1,500 rentable square feet as provided with respect to the balance
          of the Premises), i.e., two (2) parking permits based upon 6,000
          rentable square feet in the T-31 Premises. Such parking permits shall
          otherwise be made available pursuant to the terms and conditions
          recited in Section 12 of the Ninth Amendment. Upon a written request
          from Tenant, Landlord will advise Tenant as to whether any additional
          parking permits are available (as determined in Landlord's sole and
          absolute discretion), and if any parking permits are available
          Landlord shall make such permits available to Tenant.

Additional Expansion Option

    10.   Additional Expansion Option. Section 31B, Additional Expansion
          Option of the Lease, as recited in Section 10 of the Ninth Amendment,
          is hereby deleted in its entirety and the following substituted
          therefor;

          "B. Additional Expansion Option. Provided Tenant is not in default of
          its obligations under the Lease, beyond the expiration of any
          applicable grace period, either at the time Tenant exercises the
          option described below or on the commencement date of the Lease with
          respect to the




<PAGE>
                                      -7-

     Additional Expansion Premises (as defined below), and provided that Tenant
     has exercised its option to extend the Extended Term as provided in
     Paragraph 9 of the Ninth Amendment, and provided Tenant has not assigned
     this Lease or sublet all or any portion of the Extended Premises, as so
     expanded, Tenant shall have the additional option (the "Additional Option")
     to lease during the Option Term 22,090 rentable square feet of space
     located on the 31st floor of the Building and outlined on Exhibit A-4
     attached hereto and incorporated by reference (the "Additional Expansion
     Premises") commencing on the Option Term Commencement Date. If Tenant
     elects to exercise the Additional Option, simultaneously with the giving of
     Tenant's notice to extend the Extended Term, Tenant will give Landlord
     written notice of Tenant's election to exercise the Additional Option at
     least twelve (12) months, but not more that fourteen (14) months, prior to
     the Option Term Commencement Date. The Additional Expansion Premises will
     be leased to Tenant upon the same terms and conditions as contained in the
     Lease, except that Base Rent for the Additional Expansion Premises, which
     shall be included with the Extended Premises, shall be determined in
     accordance with the provisions of Paragraph 9 of the Ninth Amendment. Upon
     the commencement of the term of the Lease for the Additional Expansion
     Premises, the Additional Expansion Premises shall automatically become a
     part of the Extended Premises.

          In the event that the Additional Option is duly exercised, Landlord
     and Tenant agree to enter into an amendment to this Lease to confirm such
     exercise and to document all changes to the Lease, as amended, resulting
     from the exercise of such option and all references contained in this Lease
     to the Extended Premises shall be construed to refer to the original
     Extended Premises, as expanded pursuant to Section 31(a) hereof, as further
     expanded by the exercise of the aforesaid Additional Option, whether or not
     specific reference thereto is made in the Ninth Amendment. In exercising
     its option hereunder, Tenant acknowledges that time is of the essence.
     Failure of Tenant to exercise the Additional Option on or before the date
     specified above shall constitute a waiver by Tenant of all rights under
     such option. At such time as Tenant leases the Additional Expansion
     Premises pursuant to the provisions of this Section 31(b), Tenant's
     Proportionate Share of Ownership Taxes shall be increased as provided in
     Paragraph 5 of the Ninth Amendment and Tenant's obligations to pay rent
     adjustments for Operating Expenses shall be adjusted as provided in Section
     2(b) of the Lease."

11.  No further Expansion Options. Tenant acknowledges that it has no further
     expansion options other that the Additional Option to lease the Additional
     Expansion Premises referenced in the preceding Section 10 of this Fifteenth
     Amendment.
<PAGE>
                                      -8-

Right of First Opportunity

     12. Right of First Opportunity.

         (a)  Exercise.  From the date hereto through and including April 25,
         2008, Tenant shall have a "Right of First Opportunity" to lease the
         22,090 Rentable Square Feet of space located on the 31st floor of the
         Building and outlined on Exhibit A-4 attached hereto and incorporated
         by reference which Landlord offers to lease to any unrelated third
         party (the "First Opportunity Space"); provided, however, Tenant shall
         not have this Right of First Opportunity if Landlord plans to use,
         lease, or make available such portion of the First Opportunity Space to
         itself or to any entity controlled by, controlling, or under common
         control with Landlord or to a third party engaged in a special project
         for Landlord (each of the foregoing is referred to as a "Landlord
         Affiliate").

              Landlord will notify Tenant of its plans to offer to lease the
         First Opportunity Space to any unrelated third party other than a
         Landlord Affiliate. Landlord's notice shall specify the date of
         availability, rent, allowances, and all other material terms and
         conditions which will apply to such space.  The term of the Lease with
         respect to the First Opportunity Space shall be coterminous with the
         Term of this Lease with respect to the Premises.  Tenant will notify
         Landlord within fifteen (15) days of Landlord's notice if Tenant wishes
         to lease such space from Landlord on the terms and conditions so
         specified and otherwise on substantially the same terms and conditions
         as contained in the Lease.  If Tenant notifies Landlord that it wishes
         to lease the First Opportunity Space, Landlord and Tenant shall execute
         an agreement incorporating such terms and conditions.  If Tenant fails
         to notify Landlord within said fifteen (15) day period that Tenant
         wishes to lease such First Opportunity Space, Landlord shall be
         entitled to lease such space to a third party at an effective rent,
         considering all pertinent aspects of Landlord's proposed terms such as
         concessions, allowances, broker fees and any other costs to Landlord,
         no more favorable than that offered to Tenant; provided, however, if
         after negotiations with any such third party, Landlord desires to lease
         such space at an effective rent or on other terms which are materially
         more favorable than those offered to Tenant, Landlord will notify
         Tenant, which notice shall include all material terms and conditions of
         Landlord's proposed lease to such third party, and Tenant will notify
         Landlord within five (5) business days of Landlord's notice if Tenant
         wishes to Lease such space from Landlord on the terms and conditions so
         specified.  If Tenant fails to notify Landlord within said five (5)
         business day period that Tenant intends to lease such First Opportunity
         Space, Landlord shall be entitled to lease such space to a third party
         at an effective rent, considering all pertinent aspects of Landlord's
         proposed terms such as concessions, allowances, broker fees and any
         other costs to Landlord, no more favorable than that offered to Tenant.
         If Landlord does not enter into such a lease for the First Opportunity
         Space with another tenant within eighteen (18) months after Landlord's
<PAGE>
                                      -9-


          original notice to Tenant, then Tenant's rights under this Section 12
          shall be reinstated.

          (b)  Conditions Precedent to Exercise.  Notwithstanding any contrary
          provisions of this Section 12 or any other provision of this Lease,
          any Right of First Opportunity shall be void and of no effect unless
          on the date Tenant notifies Landlord that it is exercising the Right
          of First Opportunity and on the commencement date for such First
          Opportunity Space (i) this Lease is in full force and effect, (ii) no
          Event of Default on the part of Tenant has occurred and is continuing
          under this Lease, and (iii) Tenant shall not have assigned this Lease
          nor sublet any portion of the Premises to any entity or entities other
          than a Tenant Affiliate; provided, however, that Landlord reserves the
          right to waive the provisions of this Section 12.


Miscellaneous

      13. Storage Space.  Section 11 - Storage Space of the Ninth Amendment
          is hereby deleted in its entirety.

      14. T-31 and T-32 Internal Staircase.  During the Extended Term of the
          Lease, provided Tenant is not in default of its obligations under the
          Lease, beyond the expiration of any applicable grace period, Tenant
          shall have the right to construct an internal staircase for the
          exclusive use and enjoyment of Tenant, which staircase may connect
          those portions of the 32nd and 31st floors occupied by Tenant;
          provided that the construction of such internal staircase shall be
          performed by Tenant in compliance with the requirements of Section 10B
          of the Lease.

              At any time commencing six (6) months prior to the expiration of
          the Extended Term of the Lease or at any time after a default by
          Tenant under the Lease which remains uncured beyond any applicable
          grace period), upon demand from Landlord, Tenant shall pay to Landlord
          as additional rent, the costs estimated by Landlord to cap the
          internal staircase constructed by Tenant and to restore the 32nd and
          31st floors to their condition prior to the installation of the
          internal staircase, provided, however that if Landlord does not in
          fact commence capping the staircase and restoring the floors within
          one (1) year from the expiration of the Term then Landlord shall
          refund such costs previously paid by Tenant above.

      15. Miscellaneous. Except as herein expressly modified all of the terms
          and conditions of the Lease shall be and remain in full force and
          effect, provided, however, if and to the extent that any of the
          provisions of this Fifteenth Amendment conflict with or are otherwise
          inconsistent with any of the provisions of the Lease, the provisions
          of this Fifteenth Amendment shall prevail.
<PAGE>
                                      -10-



IN WITNESS WHEREOF, Landlord and Tenant have caused this Fifteenth
Amendment to be duly executed under seal as of the day first above written.

                                      LANDLORD:

                                      JOHN HANCOCK LIFE
                                      INSURANCE COMPANY



                                      By: /s/ Paul M. Crowley
                                      ----------------------------
                                      Paul M. Crowley
                                      Vice President

                                      TENANT:

                                      CHARLES RIVER ASSOCIATES,
                                      INCORPORATED

                                      By: /s/ Michael J. Tubridy
                                      ----------------------------
                                         Title: CFO

Exhibits:

Exhibit A-1    T-32 Premises
Exhibit A-2    T-33 Premises
Exhibit A-3    T-31 Premises
Exhibit A-4    Additional Expansion Premises/First Opportunity Space


<PAGE>
EXHIBIT A-4

                                  [FLOORPLAN]




[Exhibits A-1 through A-4 consist of floor plans for office space described in
the lease.]



















<PAGE>
EXHIBIT A-1

                                  [FLOORPLAN]


[Exhibits A-1 through A-4 consist of floor plans for office space described in
the lease.]
<PAGE>
EXHIBIT A-2

                                  [FLOORPLAN]




[Exhibits A-1 through A-4 consist of floor plans for office space described in
the lease.]
<PAGE>
EXHIBIT A-3

                                  [FLOORPLAN]



[Exhibits A-1 through A-4 consist of floor plans for office space described in
the lease.]