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                                                                   EXHIBIT 10.20

                        AGREEMENT FOR EXERCISE OF OPTION

Pursuant to Section 15.1 and 15.2 of the Lease Agreement dated as of April 1,
1995, (the Lease) between the NATIONAL FIRE PROTECTION ASSOCIATION (LANDLORD)
and ATLANTIC DATA SERVICES (TENANT) the Landlord and Tenant hereby agree on the
exercise of the "Option to Extend" as set out in those sections.

Pursuant to said Sections 15.1 and 15.2 of the Lease, the term of the Lease is
hereby extended for the Extended Term as defined in said Section 15.1, except as
hereinafter set out.

1.   Notwithstanding any provisions or formulas for determining the rent for the
     Extended Term, the Basic Rent for the Extended Term, as that term is
     referenced in Section 15.2, is hereby agreed as follows:

               YEAR #         BASIC RENT (AS DEFINED IN SECTION 1.2)
               ------         --------------------------------------

                 1                           $23.00
                 2                           $24.00
                 3                           $25.00
                 4                           $26.00
                 5                           $27.00

2.   The Definitions of "Base Operating Expenses," and "Base Taxes" as contained
     in Section 1.2 of the Lease are hereby deleted and replaced with the
     following:

               Base Operating Expenses:  Actual 2000 Operating Expenses
               Base Taxes:  Actual Fiscal Year 2000 Taxes

3.   The Landlord shall provide the Tenant with an allowance of $3.00 per square
     foot of space in the existing Leased Premises, under the Lease as amended.
     Such allowance shall, at the discretion of the landlord, be in the form of
     a payment by the Landlord to the contractor undertaking any renovation or
     similar work as requested by the Tenant, in accordance with the applicable
     provisions of the Lease. Any and all other costs of renovation similar work
     shall be the responsibility of the Tenant.

4.   The Landlord shall provide the Tenant with an allowance of $10.00 per
     square foot of space added to the Lease Premises, during the Extended Term.
     Such allowance shall, at the discretion of the Landlord, be in the form of
     a payment by the Landlord to the contractor undertaking any renovation or
     similar work as requested by the Tenant, in accordance with the applicable
     provisions of the Lease. Any and all other costs of renovation similar work
     shall be the responsibility of the Tenant.

5.   Notwithstanding the general continued effect of all provisions of the Lease
     in accordance with the said Section 15.1 and 15.2, the parties expressly
     agree that Section 14.24 regarding the Right of First Refusal, shall
     continue to be effective during the Extended Term.

6.   Pursuant to Section 15.1 of the Lease, the Extended Term shall commence, on
     the day immediately succeeding the expiration date of the Initial Term and
     ending at the close of the day on the last day of the sixtieth calendar
     month thereafter. Notwithstanding such effective date, all obligations to
     undertake the Extended Term, shall be effective immediately and shall
     continue throughout the said Extended Term.



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Signed the 23rd day of November 1999.

/s/ National Fire Protection Association       /s/ Atlantic Data Services, Inc.
------------------------------------------     ---------------------------------
NATIONAL FIRE PROTECTION ASSOCIATION           ATLANTIC DATA SERVICES, INC.
LANDLORD                                       TENANT


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