Exhibit 10.20

FIRST AMENDMENT TO
PURCHASE AND SALE AGREEMENT
(300-306 W. FAYETTE STREET)

        THIS FIRST AMENDMENT TO PURCHASE AND SALE AGREEMENT (this “First
Amendment”) is made, and shall be effective for all purposes, as of September 7,
2004 by and between PKLB Limited Partnership, a Maryland limited partnership
(“Seller”), and The Kevin F. Donohoe Company, a Pennsylvania corporation
(“Purchaser”).

RECITALS:

        R-1.         Seller and Purchaser entered into a Purchase and Sale
Agreement dated as of July 26, 2004 (the “Original Agreement”). Unless otherwise
provided in this First Amendment, all capitalized terms shall have the same
meaning as defined in the Original Agreement.

        R-2.         Seller and Purchaser desire to amend the Original Agreement
as hereinafter set forth.

        IN CONSIDERATION of the mutual covenants and agreement contained in the
Original Agreement and this First Amendment, and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
Purchaser and Seller hereby covenant and agree as follows:

        1.         Incorporation of Recitals.    The foregoing Recitals are
incorporated in this First Amendment and made a part hereof by this reference to
the same extent as if set forth herein in full.

        2.         Amendment of Original Agreement.    The Original Agreement is
hereby modified to extend the time and date of expiration of the Inspection
Period to 5:00 PM (E.S.T.) on September 20, 2004.

        3.         Ratification of Agreement.    Except as set forth in this
First Amendment, all the terms and conditions contained in the Original
Agreement are hereby ratified and shall remain in full force and effect. In the
event that any of the terms, conditions and provisions of this First Amendment
shall conflict with any of the terms, conditions and provisions of the Original
Agreement, then, and in such event, the terms, conditions and provisions of this
First Amendment shall prevail and be controlling.

        4.         Effective Date of Amendment.    The effective date of this
First Amendment shall be September 7, 2004.

        5.         Counterparts.    This First Amendment may be executed in any
number of counterparts, each of which shall be deemed an original, and all of
which, when taken together, shall be deemed to be a single instrument.

        IN WITNESS WHEREOF, and intending to be legally bound, the undersigned
have duly executed this First Amendment under seal.

WITNESS/ATTEST:

/s/  Douglas R. Veasey

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/s/  Linda L. Reeves Kenner

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PURCHASER:

THE KEVIN F. DONAHOE COMPANY, INC.

By:  /s/ Henry B. Glover, Jr.

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Name:  Henry B. Glover, Jr.

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Title:  Vice President

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SELLER:

PKLB LIMITED PARTNERSHIP

By:  BASi Maryland, Inc., General Partner

By:  /s/ Michael Silvon

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Name:  Michael Silvon

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Title:  Secretary

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