Document:

<PAGE>

                                                                    EXHIBIT 10.7

                           PURCHASE AND SALE AGREEMENT

                                     BETWEEN

                   ARMADA/HOFFLER INVESTMENT PROPERTIES, L.P.
                                    "SELLER"

                                       AND

                           COLUMBIA EQUITY TRUST, INC.
                                   "PURCHASER"

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                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                         PAGE
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<S>  <C>                                                                 <C>
1.   Purchase and Sale of the Property..............................       1
2.   Purchase Price and Method of Payment...........................       2
     2.1 Purchase Price.............................................       2
     2.2 Method of Payment..........................................       2
     2.3 Deposit....................................................       2
3.   Seller's Representations and Warranties........................       3
     3.1 Organization and Authority.................................       3
     3.2 Noncontravention...........................................       3
     3.3 Consents...................................................       3
     3.4 Ownership..................................................       4
     3.6 Condemnation...............................................       4
     3.7 Litigation or Proceedings..................................       4
     3.8 Compliance; Notice of Violations...........................       4
     3.9 Liens......................................................       4
     3.10 Lease.....................................................       5
     3.11 Service Contracts.........................................       5
     3.12 No Actions................................................       5
     3.13 Existing Indebtedness.....................................       5
     3.14 Absence of Bankruptcy.....................................       6
     3.15 Driveways and Access......................................       6
     3.16 Utilities.................................................       6
     3.17 Underground Storage Tanks.................................       6
     3.18 Property Information......................................       6
     3.19 Lease Guaranty............................................       6
     3.20 Deed Restriction/Purchase Option..........................       6
     3.21 Zoning....................................................       6
4.   Purchaser's Representations and Warranties.....................       7
     4.1 Organization and Authority.................................       7
     4.2 Noncontravention...........................................       8
     4.3 Litigation or Proceedings..................................       8
     4.4 Consents...................................................       8
5.   Inspection; Condition of Property and Title....................       8
     5.1 Right of Inspection........................................       8
     5.2 Inspection Period..........................................       9
     5.3 "As-Is and Where Is Condition".............................      10
     5.4 Title Examination..........................................      10
     5.5 Assumption of Existing Indebtedness........................      10
6.   Conditions Precedent to Closing................................      10
     6.1 Purchaser's Conditions Precedent to Closing................      10
     6.2 Failure of Condition to Purchaser's Obligations............      12
</TABLE>

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                               TABLE OF CONTENTS
                               -----------------
                                   CONTINUED...

<TABLE>
<CAPTION>
                                                                        PAGE
                                                                        ----
<S>  <C>                                                                <C>
7.   Closing........................................................      12
8.   Seller's Deliveries............................................      13
     8.1 Deed                                                             13
     8.2 Assignment of Lease and Service Contracts..................      13
     8.3 Seller's Affidavits........................................      13
     8.4 FIRPTA Affidavit...........................................      13
     8.5 Resolutions................................................      13
     8.6 Bill of Sale...............................................      13
     8.7 Possession; Keys...........................................      14
     8.8 Original Documents.........................................      14
     8.9 Files......................................................      14
     8.10 Notice of Sale............................................      14
     8.11 Termination of Management Agreement.......................      14
     8.12 Termination of Leasing Agreement..........................      14
     8.13 General Ledgers...........................................      14
     8.14 Other Documents...........................................      14
9.   Purchaser's Closing Obligations................................      14
10.  Settlement Charges; Prorations and Adjustments.................      14
     10.1 Allocation of Settlement Charges..........................      14
     10.2 Prorations and Adjustments................................      14
     10.3 Release of Closing Escrow.................................      16
11.  Condemnation and Risk of Loss..................................      16
12.  Default Provisions; Remedies...................................      16
     12.1 Purchaser's Default.......................................      17
     12.2 Seller's Default..........................................      17
13.  Obligations of Seller Pending Closing..........................      17
     13.1 Occupancy at Closing......................................      17
     13.2 Leasing...................................................      17
     13.3 Maintenance and Operation of Property.....................      18
     13.4 No Action.................................................      18
     13.5 Additional Deliveries.....................................      18
     13.6 Scheduled Payments of the Existing Indebtedness...........      18
14.  Miscellaneous Provisions.......................................      18
     14.1 Completeness and Modification.............................      18
     14.2 Additional Documents......................................      18
     14.3 Severability..............................................      18
     14.4 Cumulative Remedies.......................................      18
     14.5 Construction..............................................      19
     14.6 Pronouns..................................................      19
     14.7 Binding Effect; Assignment................................      19
     14.8 Waiver; Modification......................................      19
     14.9 Governing Law.............................................      19
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                               TABLE OF CONTENTS
                               -----------------
                                   CONTINUED...

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<CAPTION>
                                                                        PAGE
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<S>  <C>                                                                <C>
     14.10 Headings.................................................      19
     14.11 Exhibits.................................................      19
     14.12 Counterparts.............................................      19
     14.13 Notices..................................................      19
     14.14 Section 1031 Exchange....................................      20
     14.15 Business Day.............................................      20
     14.16 Survival.................................................      20
     14.17 Attorneys' Fees..........................................      20
     14.18 Waiver of Jury...........................................      21
     14.19 Brokerage Commission.....................................      21
     14.20 Confidentiality..........................................      21
     14.21 Standstill Period........................................      21
</TABLE>

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                           PURCHASE AND SALE AGREEMENT

      THIS PURCHASE AND SALE AGREEMENT ("AGREEMENT") is made and entered into as
of the 15th day of March, 2006, by and between ARMADA/HOFFLER INVESTMENT
PROPERTIES, L.P., a Virginia limited partnership ("SELLER"), and COLUMBIA EQUITY
TRUST, INC., a Maryland corporation, or its permitted assigns (collectively
"PURCHASER").

                                R E C I T A L S:

      A. Seller is the fee simple owner of that certain real property located in
Reston, County of Fairfax, Virginia consisting of certain improvements known by
street address 1741 Business Center Drive, Reston, Virginia 20190 comprising
approximately 207,725 square feet of land and containing approximately 41,357
net rentable square feet of office space in a building (the "Building") located
in the Lake Fairfax Business Center, such real property being more particularly
described on Exhibit A attached hereto; and all right, title and interest of
Seller, if any, that is appurtenant to the real property described on Exhibit A
in and to the following: any land lying in the bed of any existing, dedicated
street, road or alley, all strips and gores adjoining thereto and all
appurtenances, rights, easements, rights-of-way, covenants, tenements,
hereditaments and other rights incident thereto, including, without limitation,
any right or option to acquire or benefit from any future easement or
right-of-way to the extent that such rights and interests may benefit such real
property (collectively, the "LAND"), together with all improvements situated
thereon and all right, title and interest of Seller in and to all other
improvements, driveways, landscaping, paving, walkways, plumbing and heating
pipes and fixtures situated thereon that they may benefit such improvements,
situated thereon and/or used in connection therewith to the extent that they may
benefit such improvements (collectively, the "IMPROVEMENTS"), and, to the extent
assignable, any leases, contract rights, escrow or security deposits, utility
agreements, guarantees, licenses, approvals, amounts held in reserve by the
holder of the Existing Indebtedness (defined below) with respect to the
Improvements; certificates of occupancy, plans and specifications, logos,
permits, warranties or other rights related to the development of, construction
of, ownership or, or use and operation of, the real property (all such items
being collectively referred to as the "INTANGIBLES"), and all furniture,
fixtures and equipment and other items of personal property owned by Seller and
located in or on the real property, as described in Exhibit B attached hereto
and made a part hereof (collectively, the "PERSONALTY") (the Land and
Improvements, together with the Intangibles and Personalty, being hereinafter
sometimes referred to collectively as the "PROPERTY");

      B. Purchaser desires to purchase the Property, and Seller desires to sell
the Property, all pursuant to the following terms.

      NOW, THEREFORE, for and in consideration of the premises and mutual
covenants and agreements herein contained, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto agree as follows:

      1. PURCHASE AND SALE OF THE PROPERTY. Seller agrees to sell and transfer
the Property and its right, title and interest in the Lease (hereinafter
defined), and Purchaser agrees to purchase the Property, together with all of
Seller's right, title and interest in the Lease, pursuant to the terms and
conditions set forth herein.

<PAGE>

      2. PURCHASE PRICE AND METHOD OF PAYMENT.

            2.1 PURCHASE PRICE. The purchase price for which the Seller agrees
to sell and assign the Property (including Seller's interests in the Lease as
aforesaid) and which the Purchaser agrees to pay or deliver to the Seller,
subject to the terms and conditions set forth herein, shall be equal to ELEVEN
MILLION FIVE HUNDRED SEVENTY-FIVE THOUSAND DOLLARS ($11,575,000.00) (the
"PURCHASE PRICE") to be paid as described in Section 2.2 hereof.

            2.2 METHOD OF PAYMENT. The Purchase Price shall be payable by
Purchaser as follows: (i) Purchaser shall, at its option, either assume or
defease the indebtedness outstanding as of the Closing Date (hereinafter
defined) owed by Seller to holder of a certain Promissory Note, dated June 1,
1999, in the original principal amount of $8,800,000.00 made by The Advance
Group/Lake Fairfax, L.L.C. payable to NationsBank, N.A. (the Note")(the current
holder(s) of the Note and its servicers are collectively referred to as the
"EXISTING LENDER"), and secured by the Property and more particularly described
on Exhibit C hereto (the "EXISTING INDEBTEDNESS"); Purchaser shall be
responsible for the assumption fees or, in the event of a defeasance, any
pre-payment penalties and all costs and expenses of such defeasance, and
reasonable costs and expenses of Existing Lender (including reasonable
attorney's fees) related to the assumption or defeasance of the Existing
Indebtedness (the "LOAN FEES") and the amount of the Loan Fees shall not be
deducted from the Purchase Price or be considered to be a part of the Existing
Indebtedness assumed by Purchaser; and (ii) the balance after application of the
assumption or the defeasance amounts described in (i) above, as further adjusted
to account for any reserves held by Existing Lender, in the case of an
assumption, and any prorations and adjustments required hereunder, and minus the
Deposit (below defined) shall be paid by Purchaser in escrow to the Escrow Agent
(below defined) in immediately available U.S. funds.

            2.3 DEPOSIT. Within three (3) business days following the Effective
Date, Purchaser shall deposit with Commercial Title Group, Inc. or another
escrow agent acceptable to Purchaser and Seller (the "ESCROW AGENT") in cash,
One Hundred Fifty Thousand Dollars ($150,000.00) (the "GOOD FAITH DEPOSIT"). The
Good Faith Deposit shall become non-refundable, except as otherwise provided in
this Agreement, in the event the Agreement is not terminated prior to the
expiration of the Inspection Period (below defined). If the Agreement is
terminated prior to the expiration of the Inspection Period, the Good Faith
Deposit will be fully refunded to Purchaser. If Purchaser does not terminate the
Agreement, then within three (3) business days following the expiration of the
Inspection Period, Purchaser will deposit with Escrow Agent the additional sum
of One Hundred Fifty Thousand Dollars ($150,000.00) (the "EARNEST MONEY,"
collectively with the Good Faith Deposit, being hereinafter referred to as the
"DEPOSIT"). The Deposit will be non-refundable except for a default by Seller
under the Agreement, a material casualty, a condemnation, or a failure to meet a
closing condition. As used herein, the term "DEPOSIT" shall include the Deposit
and all interest earned on the Deposit.

            2.4. ESCROW AGENT. The Escrow Agent shall not be liable for any acts
or omissions at any time unless caused by the gross negligence or willful
malfeasance of the Escrow Agent with respect to the escrow established herein.
If a dispute arises between the parties as to the disposition of the Deposit,
the Escrow Agent shall: (a) hold the Deposit until the Escrow Agent has received
releases signed by all parties to the transaction authorizing disposition of the
Deposit, or (b) hold the Deposit until such time as one of the parties to the
transaction files suit and the court in which the suit is filed orders the
disbursement of the

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Deposit, or (c) deliver such Deposit into the court by filing an Interpleader
Action. In the event of any litigation between Seller and Purchaser concerning
the Deposit, Escrow Agent's sole responsibility may be satisfied, at Escrow
Agent's option, by delivering the Deposit into the court in which such
litigation is pending, and Purchaser and Seller agree that upon deliverance of
such Deposit into court, neither Purchaser nor Seller shall have any further
right, claim, demand, or action against the Escrow Agent. In the event any
dispute arises under this Agreement between Seller and Purchaser resulting in
the Escrow Agent being made a party to any litigation, Seller and Purchaser,
jointly and severally, shall indemnify the Escrow Agent for all costs, and
reasonable attorneys' fees and legal expenses incurred by the Escrow Agent as a
result thereof, provided that such litigation does not result in a judgment
against the Escrow Agent for acting improperly under this Agreement.
Notwithstanding anything to the contrary contained in this Section 2.4, Escrow
Agent and Seller acknowledge and agree that Purchaser has the unilateral right
to receive a refund of the Deposit pursuant to Section 5.2.

      3. SELLER'S REPRESENTATIONS AND WARRANTIES. In order to induce Purchaser
to enter into this Agreement and to purchase the Property, Seller makes the
following representations and warranties, each of which being true and correct
in all material respects as of the date hereof and, to the extent such
representations and warranties shall still be true and correct in all material
respects on the Closing Date, will reaffirm such on the Closing Date. To the
extent Seller discovers such representations and warranties are no longer true
and correct in all material respects, Seller shall, upon such discovery, provide
prompt written notice to Purchaser, with sufficient detail in order to
reasonably and fully advise Purchaser of any such change. (However, such a
notice shall not effect Purchaser's right to terminate this Agreement under
Section 6.2 hereof.)

            3.1 ORGANIZATION AND AUTHORITY. Seller has full power and authority
to enter into this Agreement, to sell the Property to Purchaser and to otherwise
perform its obligations hereunder. Seller further represents to Purchaser that
the execution, delivery and performance of this Agreement, the fulfillment of
and compliance with the terms and provisions hereof and the due consummation of
the transactions contemplated hereby have been duly and validly authorized and
approved by all requisite organizational action, all of which are in full force
and effect. The purchase and sale of the Property pursuant to this Agreement
(and the consummation of the transactions contemplated herein) shall not violate
any law, ordinance, judgment, decree or order to which Seller or the Property is
subject. Seller is not a "FOREIGN PERSON" as that term is defined by Section
1445 of the Internal Revenue Code of 1986, as amended (the "CODE").

            3.2 NONCONTRAVENTION. Neither the entry into nor the performance of,
or compliance with, this Agreement by Seller has resulted, or will result, in
any violation of, or default under, or result in the acceleration of, any
obligation under any existing organizational documents or agreements, mortgage,
indenture, lien agreement, note, contract, permit, judgment, decree, order,
restrictive covenant, statute, rule, or regulation applicable to Seller.

            3.3 CONSENTS. Each consent, approval, authorization, order, license,
certificate, permit, registration, designation, or filing by or with any
governmental agency or body necessary for the execution, delivery, and
performance of this Agreement or the transactions contemplated hereby by Seller
has been obtained or will be obtained on or before the Closing Date. The tenant
under the Lease, Chubb Computer Services, Inc., has provided Seller with a
written waiver of its rights to purchase the Property, a copy of which waiver is
attached hereto and made a part hereof as Exhibit D.

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            3.4 OWNERSHIP. Seller is the sole, fee simple owner of full legal,
equitable and beneficial title to the Property, free and clear of liens and
encumbrances other than the Permitted Exceptions (defined below) and the lien
securing the Existing Indebtedness. To the best of Seller's actual knowledge,
Seller is not in default of any of its obligations under the Permitted
Exceptions, except a potential contingent liability to build an access road as
set forth under that certain letter agreement, dated May 28, 1999, between LFBC
Ten Limited Partnership, Lake Fairfax Seven Limited Partnership and The Advance
Group/Lake Fairfax, LLC.

            3.5. HAZARDOUS WASTES. With respect to the Property (including,
without limitation, the soil and ground water underneath the Improvements), no
summons, citation, directive, notice or complaint issued by the United States
Environmental Protection Agency or other federal or local Government authority
has been received by Seller, its employees or to Seller's knowledge, its agents,
concerning any alleged violations of any environmental laws and regulations or
any investigation or request for information relating to the handling,
packaging, transportation, treatment, storage or disposal of Hazardous
Substances on-site or when transported off-site. To Seller's knowledge, the
Property is in compliance with all laws, regulations, orders, decrees and
agreements relating to Hazardous Substances and there are no Hazardous
Substances on, at or under the Property as of the date hereof. The term
"HAZARDOUS SUBSTANCES" means any "HAZARDOUS CHEMICAL," "HAZARDOUS SUBSTANCE" or
similar term as defined in the Comprehensive Environmental Response,
Compensation and Liability Act of 1980, as amended (42 U.S.C. Section 9601 et
seq.), and all rules and regulations thereunder or in any other applicable
federal, state, or local law, rule or regulation dealing with environmental
protection (including but not limited to petroleum products). For the purposes
of this Agreement, the term Hazardous Substances also includes radon, petroleum
and petroleum products, asbestos and asbestos products, and mold and mildew.

            3.6 CONDEMNATION. No taking by power of eminent domain or
condemnation proceeding or similar proceeding has been instituted or, to
Seller's knowledge, threatened for the permanent or temporary taking or
condemnation of all or any portion of the Property.

            3.7 LITIGATION OR PROCEEDINGS. Seller has not received any notice
and has no knowledge of any action, suit, proceeding or claim affecting the
Property, or any portion thereof, relating to or arising out of the ownership,
operation, use or occupancy of the Property pending, threatened or being
prosecuted in any court or by or before any federal, state, county or municipal
department, commission, board, bureau or agency or other governmental
instrumentality.

            3.8 COMPLIANCE; NOTICE OF VIOLATIONS. Seller has not received any
written notice of any violation of any law, rule, regulation, order,
requirement, code, ordinance, statute or regulation issued by any Government
agency, board, commission, authority or other Government entity, or any
insurance board of underwriters, or of any action in any court or in any
Government or administrative body on account thereof, against or affecting the
zoning, use, development, maintenance, condition or operation of the Property or
any part thereof.

            3.9 LIENS. No labor has been performed or materials furnished at the
request or direction of Seller that could result in a materialman's or
mechanic's lien filed against the Property except as shall be fully paid or
released prior to Closing. All real estate taxes on the

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Property which have become due and payable prior to Closing have been or will be
paid by Closing.

            3.10 LEASE. There are no leases, subleases, lease guaranties,
assignments, license agreements or other occupancy agreements for the Property
binding upon the Purchaser or its successors other than the Lease identified on
Exhibit E attached hereto (the "LEASE") and made a part hereof. To the best of
Seller's actual knowledge, the Lease is in full force and effect and shall not
be further extended, modified or amended in any manner prior to Closing without
the Purchaser's consent, which shall not be unreasonably withheld, conditioned
or delayed. To Seller's knowledge, neither landlord nor tenant is in default
under the Lease, and there are no other obligations of the landlord pertaining
to the Property except as expressly set forth in the Lease, Service Contracts,
Loan Documents and other matters disclosed in this Agreement. The tenant under
the Lease has not prepaid rent thereunder except for Property operating
expenses. To the knowledge of Seller, no controversy, claim, dispute or
disagreement exists between the parties to the Lease and no event has occurred
which, with the giving of notice or the passage of time, or both, would
constitute a default under the Lease. To the best of Seller's actual knowledge,
the Lease is valid and enforceable in accordance with its terms and in full
force and effect. Seller has not sent written notice of termination to the
tenant under the Lease. Seller has not received written notice of termination,
default, or challenge to the validity of the Lease from the tenant under the
Lease. There is no security deposit or other deposits or outstanding tenant
improvement obligations under the Lease, except as expressly set forth on
Exhibit E. There are no brokerage, leasing or other commissions payable with
respect to the Lease as of the date hereof, and at Closing, there shall be no
such commissions payable, whether with respect to the present term thereunder or
any renewal term, except as expressly set forth on Exhibit E.

            3.11 SERVICE CONTRACTS. All service, maintenance, supply,
management, leasing contracts or other agreements ("SERVICE CONTRACTS") which
affect the Property are shown on Exhibit F attached hereto and made a part
hereof. To Seller's knowledge, Seller is not in default under any of the Service
Contracts and to its knowledge no other parties to any of the Service Contracts
are in default thereunder. On or before the expiration of the Inspection Period,
Purchaser shall notify Seller which of the Service Contracts, if any, Purchaser
elects to assume at Closing and Purchaser and Seller will enter into a mutually
acceptable assignment and assumption agreement at Closing for all such assumed
Service Contracts. Those Service Contracts not assumed by Purchaser shall be
terminated by Seller on or before Closing, as of the date of Closing. True and
complete copies of the Service Contracts have been or will be delivered to
Purchaser by or on behalf of Seller within five (5) days of the Effective Date
and, to Seller's knowledge, all the Service Contracts are in full force and
effect and none of them has been further modified, amended or extended.

            3.12 NO ACTIONS. Seller shall not take any action or cause or permit
by its agents or employees any action to be taken which would cause any of the
representations or warranties contained or incorporated in this Agreement to be
untrue as of the Closing Date. Seller agrees to notify Purchaser promptly in
writing of any event or condition of which Seller becomes aware which occurs
prior to Closing hereunder and which causes a material change in the truth of
any of the representations or warranties contained herein.

            3.13 EXISTING INDEBTEDNESS. To the extent not previously provided or
made available to Purchaser, Seller represents that copies of the Existing
Indebtedness shall be provided to Purchaser within three (3) business days
following the Effective Date hereof. Seller

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<PAGE>

represents and warrants to the Purchaser that, to the best of Seller's actual
knowledge, (i) there are no defaults existing, nor has any event occurred which,
with the giving of notice or the passage of time, or both, would constitute a
default, under any loan documents securing or otherwise delivered by Seller in
connection with the Existing Indebtedness; and (ii) the Existing Indebtedness is
assumable subject to the terms of the Existing Indebtedness. As of March 6,
2006, to the best of Seller's actual knowledge, (a) the outstanding principal
amount of the Existing Indebtedness is $7,339,548.04, and (b) the reserves held
by the holder of the Existing Indebtedness are as follows: (i) Replacement
Reserve of $12,588.42 and (ii) Tenant Improvement Reserve of $24,087.15.

            3.14 ABSENCE OF BANKRUPTCY. Neither Seller nor any general partner
of Seller has commenced (within the meaning of any Bankruptcy Law) a voluntary
case, consented to the entry of an order for relief against it in an involuntary
case, or consented to the appointment of a custodian of it or for all or any
substantial part of its property, nor has a court of competent jurisdiction
entered an order or decree under any Bankruptcy Law that is for relief against
Seller or any of its general partners in any involuntary case or appoints a
custodian of Seller or any of its general partners or for all or any substantial
part of its or their property.

            3.15 DRIVEWAYS AND ACCESS. Seller has no actual knowledge of any
federal, state, county, municipal or other governmental plans to change the
highway or road system in the vicinity of the Property or to restrict or change
access from any such highway or road to the Property.

            3.16 UTILITIES. To the best of Seller's actual knowledge, (a) all
water, sewer, gas, electricity, telephone and other utilities required for the
use, occupancy, operation and maintenance of the Improvements are connected
thereto and in service, are adequate to serve the normal operation of the
Property, are supplied directly to the Property by facilities of public or
private utilities, and the cost of installation and connection of such utilities
has been fully paid and (b) all public utilities required for the operation of
the Property enter the Property through lands as to which valid public or
private easements exist that will inure to the benefit of Purchaser.

            3.17 UNDERGROUND STORAGE TANKS. To the best of Seller's actual
knowledge, there are no underground storage tanks located on the Property.
Seller has not removed, or caused to be removed, any underground storage tanks
from the Property and, to the best of Seller's knowledge, no underground storage
tanks were removed from the Property before Seller acquired title to the
Property.

            3.18 PROPERTY INFORMATION. The copies of the Lease, the Guaranty
(hereinafter defined) and the Rent Roll provided or to be provided to Purchaser
are true, accurate and complete in all material respects and, to the best of
Seller's actual knowledge, the copies of the Property Information (hereinafter
defined) delivered or to be delivered by Seller to Purchaser are complete in all
material respects. Except as may otherwise be provided in the Agreement, Seller
does not represent or warrant to Purchaser the truthfulness or accuracy of any
of the Property Information and Purchaser shall rely on such Property
Information at its own risk.

            3.19 LEASE GUARANTY. The Guaranty of Lease dated September 15, 1998
(the "GUARANTY") by Federal Insurance Company (the "GUARANTOR") with regard to
the Lease is in full force and effect, has not been amended, and, to Seller's
knowledge, neither landlord nor Guarantor is in default under the Guaranty.

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            3.20 DEED RESTRICTION/PURCHASE OPTION. In connection with the
Special Warranty Deed, Building Restriction, Purchase Option and Grant of
Easements dated June 8, 1999 (the "1999 DEED") with respect to the Land by and
between Lake Fairfax Seven Limited Partnership, as Grantor, and The Advance
Group/Lake Fairfax, LLC, as Grantee, (a) to the best of Seller's actual
knowledge, the tenant under the Lease moved into the Property on or about
January 28, 2000; (b) to the best of Seller's actual knowledge, the Option to
purchase the Service Land and the Service Building (as such terms are defined in
the 1999 Deed) remains in full force and effect, and Seller will assign all of
its rights, title and interest in such Option to Purchaser upon its purchase of
the Property; and (c) Seller has not received an Exercise Notice, as defined in
the 1999 Deed.

            3.21. ZONING. To the best of Seller's actual knowledge, there are no
outstanding zoning proffers applicable to the Property or any part thereof.

      When used in this Section 3 and elsewhere in this Agreement, "TO SELLER'S
KNOWLEDGE," "TO SELLER'S ACTUAL KNOWLEDGE," "SELLER IS NOT AWARE OF," "SELLER
DOES NOT KNOW" and words of similar import mean the knowledge of (i) Shelly R.
Hampton, Seller's Director of Asset Management, and of (ii) Eric L. Smith,
Seller's asset manager, without investigation or duty of investigation, and such
words expressly do not include any constructive or imputed knowledge.

      Seller shall have the right, from time to time after the Effective Date
and at or prior to Closing, to amend its representations and warranties set
forth above due to any change in the facts outside the control of and otherwise
not caused by Seller and not actually known by Seller as of the Effective Date
by providing Purchaser with written notice thereof and providing the specific
nature of such untrue representation; provided, however, in the event that
Seller does so amend its representations or warranties (in any material adverse
respect with respect to representations and warranties not qualified by
materiality), Purchaser shall have the right, as its sole remedy for such
amendment, to terminate this Agreement, and receive a refund of the Deposit, if
Seller does not cure or otherwise correct such matter to the Purchaser's
reasonable satisfaction. Seller's representations and warranties shall survive
Closing for a period of twelve (12) months thereafter and same shall constitute
a contingent liability of Seller during such survival period. Notwithstanding
the foregoing, no representation or warranty shall be deemed to have survived
Closing, if Purchaser shall have had actual knowledge of a breach or violation
of such representation or warranty at the time of Closing and elected to proceed
to Closing notwithstanding such breach or violation.

      4. PURCHASER'S REPRESENTATIONS AND WARRANTIES. In order to induce Seller
to enter into this Agreement and to sell the Property, Purchaser makes the
following representations and warranties, each of which being true and correct
in all material respects as of the date hereof and each of which shall be true
and correct in all material respects on the Closing Date.

            4.1 ORGANIZATION AND AUTHORITY. Purchaser has full power and
authority to enter into this Agreement. Purchaser will have at Closing, full
power and authority to purchase the Property from Seller and to otherwise
perform its obligations hereunder. Purchaser further represents to Seller that
the execution, delivery and performance of this Agreement, the fulfillment of
and compliance with the terms and provisions hereof and the due consummation of
the transactions contemplated hereby will be at Closing duly and validly
authorized and approved by all requisite organizational action, all of which
will be in full force and effect. The purchase of the Property pursuant to this
Agreement (and the consummation of the transactions

                                       7
<PAGE>

contemplated herein) will not violate any law, ordinance, judgment, decree or
order to which Purchaser is subject.

            4.2 NONCONTRAVENTION. Neither the entry into nor the performance of,
or compliance with, this Agreement by Purchaser has resulted, or will result, in
any violation of, or default under, or result in the acceleration of, any
obligation under any existing organizational documents or agreements, mortgage,
indenture, lien agreement, note, contract, permit, judgment, decree, order,
restrictive covenant, statute, rule, or regulation applicable to Purchaser.

            4.3 LITIGATION OR PROCEEDINGS. Purchaser has received no notice and
has no knowledge of any action, suit, proceeding or claim affecting Purchaser
pending, threatened or being prosecuted in any court or by or before any
federal, estate, county or municipal department, commission, board, bureau or
agency or other governmental instrumentality that impairs or affects Purchaser's
ability to enter into this Agreement and perform its obligations hereunder or
that could materially and adversely affect the business, financial position, or
results of operations of the Purchaser.

            4.4 CONSENTS. Except as may otherwise be set forth in Section 6
hereof, each consent, approval, authorization, order, license, certificate,
permit, registration, designation, or filing by or with any governmental agency
or body necessary for the execution, delivery, and performance of this Agreement
or the transactions contemplated hereby by the Purchaser has been obtained or
will be obtained on or before the Closing Date.

      5. INSPECTION; CONDITION OF PROPERTY AND TITLE.

            5.1 RIGHT OF INSPECTION. Purchaser shall have the right, at its own
risk, cost and expense, at any time prior to Closing during normal business
hours (i.e. Monday through Friday from 9:00 a.m. to 5:00 p.m. (federal holidays
excepted) upon not less than twenty-four (24)) hours prior notice to Seller, and
subject to the approval of the tenant under the Lease with respect to any entry
into the leased premises (if required under the terms of the Lease), to enter,
or cause its agents or representatives to enter, upon the Property for the
purpose of making surveys, tests, test borings, inspections, investigations and
architectural, structural, economic, environmental and other studies of the
Property as Purchaser may deem desirable and to interview the tenant under the
Lease. Seller shall, within two (2) business days after the Effective Date
(unless otherwise provided on Exhibit M), forward to Purchaser all of the
documents related to the Property as set forth on Exhibit M attached hereto and
made a part hereof (the "PROPERTY INFORMATION") to the extent such Property
Information is in the possession of Seller or within Seller's reasonable
control. Seller agrees that it shall reasonably cooperate with Purchaser in
connection with any other information regarding the Property reasonably
requested by Purchaser and will provide or make available such information
during the Inspection Period and at all periods thereafter through the Closing
to the extent in Seller's possession. Purchaser shall, at Purchaser's sole cost
and expense, promptly and fully restore any damage or destruction to the
Property occurring as a result of any act or omission of Purchaser by reason of
such tests, studies or investigations. Purchaser shall indemnify, defend and
hold Seller harmless from and against all loss, cost, damage or claim (including
attorneys' fees reasonably incurred, court costs and costs of investigation)
arising out of or resulting from Purchaser's exercise of the right and privilege
granted to Purchaser contained in this Section 5.1, and the undertakings
contained in this Section 5 shall survive Closing or prior termination of this
Agreement. The parties acknowledge that Purchaser may be required to perform a
historical

                                       8
<PAGE>

audit of the Property in order to comply with Item 3-14 of Regulation S-X
promulgated under the Securities Act of 1933 and the Securities Exchange Act of
1934. Seller shall, effective as of the Closing Date, made commercially
reasonable efforts to permit Purchaser's auditors access at that location where
Seller customarily maintains its records, upon reasonable advance notice and
during normal business hours, to all of the Property's books and records and the
operating statements (certified by an officer of the general partner of Seller)
and property management balance sheets for the Property for one (1) calendar
year prior to the Closing Date and for the period from the end of the prior
fiscal year through the Closing Date. To the extent that the originals or copies
of same are not otherwise provided by Seller to Purchaser at the Closing, and to
the extent that the same are ordinarily maintained by Seller in its normal
course of business, such books and records shall include the detail general
ledger of profits and loss, accounts receivable records, rent rolls, billing
records, accounts payable records, and contracts. Purchaser's access rights
shall commence on the Closing Date and shall continue until the successful
completion of the audit and the filing of the 3-14 report with the SEC, written
notice of which shall be delivered promptly by Purchaser to Seller. The
foregoing obligation shall fully survive the Closing. Notwithstanding anything
to the contrary in the foregoing, other than providing the access to Purchaser
specified herein, Seller shall not have any liability or responsibility in
connection with or in any manner related to, directly or indirectly, any audit
required to be made by Purchaser or any compliance required of Purchaser with
any Regulation under the Securities Act of 1933 or the Securities Act of 1934.

            5.2 INSPECTION PERIOD. Purchaser's obligations under this Agreement
are subject to Purchaser's approval of the Property for Purchaser's intended use
and to satisfaction of certain other contingencies more fully described below.
Purchaser shall have the period commencing on the Effective Date and ending at 5
p.m. on that date which is thirty (30) days after the Effective Date (the
"INSPECTION PERIOD") to inspect the Property and to conduct such tests and
investigations as it deems advisable in order to determine that the Property can
be used for Purchaser's intended use. If, during the Inspection Period,
Purchaser in its sole discretion is not satisfied with its findings hereof for
any or no reason whatsoever, Purchaser shall notify Seller and Escrow Agent in
writing (prior to the expiration of the Inspection Period) in which event:

                  a. the Good Faith Deposit shall be returned to Purchaser by
Escrow Agent without any authorization by Seller;

                  b. this Agreement shall be terminated; and

                  c. the parties shall be relieved of any further obligation and
responsibility under this Agreement, subject only to the Purchaser's obligations
under Section 5.1.

It is expressly recognized and agreed by the parties that if Purchaser fails to
terminate this Agreement prior to the expiration of the Inspection Period,
Purchaser shall be deemed to have waived its termination right under this
Section 5.2, and the entire Deposit shall thereupon be deemed at risk to
Purchaser, subject to the other terms of this Agreement. Consequently, should
Purchaser wrongfully fail to settle on the Property pursuant to the terms of
this Agreement, the Deposit shall be non-refundable to Purchaser and paid to
Seller in accordance with the Default provisions below as final, liquidated
damages.

                                       9
<PAGE>

            5.3 "AS-IS AND WHERE IS CONDITION". The Purchaser acknowledges that,
except as otherwise expressly set forth herein and subject to Purchaser's rights
in Sections 5.1 and 5.2 above, it is accepting the Property "as is and where
is," in its present physical condition, which Purchaser is familiar with or has
had adequate opportunity to become familiar with. Except as specifically
provided in this Agreement, the Purchaser acknowledges that Seller has made no
representations or warranties to the Purchaser regarding the condition of the
Property.

            5.4 TITLE EXAMINATION. Purchaser shall have until the expiration of
the Inspection Period, at Purchaser's sole expense, to obtain title and survey
examinations of the Property and owner's title insurance commitments, in form
and substance, and issued by a title insurance company, acceptable to Purchaser
and subject only to those exceptions to title to the Property Purchaser agrees
to accept. If Purchaser is not satisfied with the state of title or survey
matters to the Property, Purchaser shall notify Seller of such title or survey
objections in writing ("OBJECTIONS NOTICE") prior to the expiration of the
Inspection Period. If Seller does not agree in writing ("SELLER'S RESPONSE")
within five (5) days of Seller's receipt of the Objection Notice to attempt to
cure any such title or survey objections raised by Purchaser (which Seller shall
not be obligated to do), then Purchaser may terminate this Agreement by
providing written notice thereof to Seller within five (5) days of Purchaser's
receipt of the Seller's Response or if no such written notice is received by
Purchaser within five (5) days of the date Seller's Response was due, in which
event the Deposit shall be returned to Purchaser and neither party shall have
any further rights or obligations hereunder, except as expressly provided
herein. If (i) Purchaser fails to deliver an Objections Notice, or (ii) Seller
does not agree in writing to attempt to cure any such noticed title or survey
objections and Purchaser fails to terminate this Agreement pursuant hereto,
then, in either event, Purchaser shall be deemed to have waived any such title
or survey objections and shall proceed to Closing without any reduction in the
Purchase Price, in which event the Property will be conveyed to Purchaser
subject to such title or survey objections and such title or survey objections
shall thereafter constitute "PERMITTED EXCEPTIONS" for all purposes of this
Agreement. If Seller undertakes in writing to attempt to cure any noticed title
or survey objections raised by Purchaser, but Seller is unable to cure such
title or survey objections at or prior to Closing, then, subject to Section 6.2,
Purchaser may terminate this Agreement by providing written notice thereof to
Seller, in which event the Deposit shall be returned to Purchaser and neither
party shall have any further rights or obligations hereunder.

            5.5 ASSUMPTION OF EXISTING INDEBTEDNESS. Commencing on the Effective
Date, Purchaser shall work actively and in good faith with Existing Lender to
ensure that Purchaser will be able to timely and satisfactorily assume the
Existing Indebtedness at Closing. Seller shall cooperate with Purchaser in good
faith prior to Closing in connection with such Purchaser efforts, and shall sign
such documents as may be reasonably required by Existing Lender to effectuate
such assumption. In connection therewith and as a condition to Seller's
obligations hereunder, Seller and any guarantors shall be released from any
obligations under the Existing Indebtedness which accrue after the Closing.
Purchaser shall be responsible for the Loan Fees and such amounts shall not be
deducted from the Purchase Price.

      6. CONDITIONS PRECEDENT TO CLOSING.

            6.1 PURCHASER'S CONDITIONS PRECEDENT TO CLOSING. It shall be a
condition precedent to Purchaser's obligation to make a full settlement
hereunder that each and every one of the following conditions shall exist on the
Closing Date:

                                       10
<PAGE>

                  a. REPRESENTATIONS AND WARRANTIES. Each of Seller's
representations and warranties contained herein shall be true and correct in all
material respects in the same manner and with the same effect as though such
representations and warranties had been made on and as of the Closing Date. In
addition, Seller shall have complied with its obligations under Sections 8 and
13 below as of the Closing Date.

                  b. CONDITION OF PROPERTY. Seller shall not have committed
waste or nuisance upon the Property and shall have maintained and kept the
Property (including the grounds thereof) in substantially the same order and
condition as exists as of the date hereof, normal wear, tear and obsolescence
excepted. Seller shall not cause any renovations, alterations or significant
cosmetic changes to be made at or to the Property prior to Closing except
required repairs and any alterations or changes made with Purchaser's written
consent (which consent shall not be unreasonably delayed, withheld or
conditioned). Seller shall not have undertaken or permitted any action within
Seller's control, without the consent of Purchaser, which would impair or
otherwise affect the use, ownership, acquisition or development of the Property
on or after Closing in any material, adverse respect or which would cause any of
the representations or warranties set forth herein to be untrue in any material
respect.

                  c. EXISTING INDEBTEDNESS. The Existing Indebtedness shall have
been assumed or defeased by Purchaser, and all necessary consents related to the
Existing Indebtedness (including, but not limited to the delivery of all
assumption or defeasance documents executed by Existing Lender) shall have been
received by Purchaser. Purchaser shall be responsible for any Loan Fees,
including, but not limited to, pre-payment penalties and other expenses
associated with defeasance of the Existing Indebtedness. In the event that
Purchaser elects to exercise its option to cause a defeasance of the Existing
Indebtedness, Seller shall cooperate fully with Purchaser to effectuate such
defeasance, including without limitation, by executing documents requested by
the holder of the Existing Indebtedness required to effectuate the defeasance.

                  d. TENANT ESTOPPEL CERTIFICATE. Seller shall obtain from the
tenant of the Lease and shall deliver to Purchaser at least three (3) business
days prior to Closing, a signed estoppel certificate, dated no more than thirty
(30) days prior to the Closing Date, in the form of the estoppel certificate
attached hereto and made a part hereof as Exhibit G or in the form which may be
required by the Lease. If Seller has obtained the foregoing estoppel certificate
in accordance with this subparagraph and Purchaser exercises its right pursuant
to Section 7 to extend the date of Closing, Seller shall make reasonable efforts
to update or obtain a new estoppel certificate, but such updated or new estoppel
certificate shall not be a condition to Purchaser's obligations under this
Agreement.

                  e. CC&R ESTOPPEL CERTIFICATES. Purchaser shall obtain from
each Benefited Owner (as such term is defined in the Ingress-Egress Easement and
Maintenance Agreement dated February 26, 1999 and recorded among the land
records of Fairfax County, Virginia at Deed Book 10896, Page 1139), at least
three (3) business days prior to Closing, a signed estoppel certificate, dated
no more than thirty (30) days prior to the Closing Date, in the form of the
estoppel certificate attached hereto and made a part hereof as Exhibit H-1.
Purchaser shall obtain from Lake Fairfax Business Center Owners' Association at
least three (3) business days prior to Closing, a signed estoppel certificate,
dated no more than thirty (30) days prior to the Closing Date, in the form of
the estoppel certificate attached hereto and made a part hereof as Exhibit H-2.
If Purchaser has obtained either of the foregoing estoppel certificates in
accordance

                                       11
<PAGE>
with this subparagraph and Purchaser exercises its right pursuant to Section 7
to extend the date of Closing, while Purchaser may attempt to update or obtain a
new estoppel certificate, the receipt of such update or new estoppel certificate
shall not be a condition to Purchaser's obligations under this Agreement. Seller
agrees to cooperate with Purchaser in the obtaining of the certificates required
by this paragraph. If Purchaser shall fail to obtain the foregoing certificates
prior to the Closing, Seller may extend the Closing for up to twenty (20) days
by giving Purchaser written notice of such extension prior to the originally
scheduled Closing in order to provide Seller with an opportunity to obtain such
certificates.

                  f. GUARANTOR ESTOPPEL CERTIFICATE. Seller shall obtain from
Guarantor and shall deliver to Purchaser at least three (3) business days prior
to Closing, a signed estoppel certificate, dated no more than thirty (30) days
prior to the Closing Date, in the form of the estoppel certificate attached
hereto and made a part hereof as Exhibit I or in the form which may be required
by the Guaranty. If Seller has obtained the foregoing estoppel certificate in
accordance with this subparagraph and Purchaser exercises its right pursuant to
Section 7 to extend the date of Closing, Seller shall make reasonable efforts to
update or obtain a new estoppel certificate, but such updated or new estoppel
certificate shall not be a condition to Purchaser's obligations under this
Agreement.

            6.2 FAILURE OF CONDITION TO PURCHASER'S OBLIGATIONS. In the event of
the failure of any condition precedent set forth in Section 6.1 above as of the
Closing Date, Seller shall have the right to extend the Closing Date by written
notice to Purchaser prior to the Closing Date by up to ten (10) days, in order
to attempt to satisfy such condition. In the event of the failure as of the
Closing Date (as the same may have been extended) of any condition precedent set
forth in Section 6.1 above, Purchaser, at its sole election, may, at its option,
either:

                  a. terminate this Agreement, in which event the Deposit shall
be returned to Purchaser and, if the failure of a condition precedent is under
Section 6.1 a or 6.1 b and such failure is caused by the Seller, Seller shall
reimburse Purchaser for all out-of-pocket costs actually incurred by Purchaser
in connection with the negotiation of this Agreement and the reasonable pursuit
by Purchaser of the transactions contemplated hereunder, including without
limitation, reasonable attorney's fees and all consultant's costs to investigate
the Property (collectively, the "PURSUIT COSTS") up to a maximum amount of Forty
Thousand Dollars ($40,000.00), whereupon neither party shall have any further
obligations or liabilities to the other, subject only to the obligations of the
Purchaser under Section 5.1, or

                  b. waive the condition and proceed to Closing.

     However, nothing contained herein shall be deemed to affect the rights of
Purchaser under Section 6.1 in the event Seller has breached a representation or
warranty made by Seller under this Agreement, or Seller shall default in its
obligations to settle on the Property. Notwithstanding the foregoing, the
failure of Seller to obtain any of the estoppel certificates described in
subsections d, e or f of Section 6.1 shall not be an event of default under this
Agreement.

      7. CLOSING. Prior to the end of the Inspection Period, Purchaser shall
advise Seller in writing if Purchaser elects to assume the Existing Indebtedness
or to defease the Existing Indebtedness. The purchase and sale contemplated
herein shall be consummated at a settlement ("CLOSING") which shall take place
on the date (the "CLOSING DATE") that is (i) forty-five (45) days after the
expiration of the Inspection Period, if Purchaser has elected to defease the
Existing

                                       12
<PAGE>

Indebtedness, or (ii) ten (10) business days after the Existing Lender has
approved Purchaser's assumption of the Existing Indebtedness. The Existing
Lender shall not be deemed to have approved Purchaser's assumption of the
Existing Indebtedness until the Existing Lender and Purchaser have agreed upon
the final form of all assumption documents. If Purchaser has elected to assume
the Existing Indebtedness and in the event that Existing Lender has not approved
Purchaser's assumption by the date which is forty-five (45) days after the
expiration of the Inspection Period, Purchaser shall have the right to terminate
this Agreement, upon written notice to Seller, and to receive a return of the
Deposit. If such assumption has not been approved within sixty (60) days after
the expiration of the Inspection Period, Seller shall have the right to
terminate this Agreement, upon written notice to Purchaser, and Purchaser shall
receive a return of the Deposit. The Closing shall take place during normal
business hours on the Closing Date at the offices of the Escrow Agent or at such
other location as the parties may mutually agree. Purchaser shall have the right
to extend the Closing Date by an additional thirty (30) days by posting an
additional Two Hundred Fifty Thousand Dollars ($250,000.00) as part of the
non-refundable Deposit with the Escrow Agent, upon three (3) days written notice
prior to the original Closing Date.

      8. SELLER'S DELIVERIES. Seller, with respect to the Property, shall
execute, as appropriate, and deliver to the Escrow Agent at Closing:

            8.1 DEED. Special warranty deed ("DEED") in the form attached hereto
and made a part hereof as Exhibit J, whereunder Seller grants and conveys fee
simple title to the Property.

            8.2 ASSIGNMENT OF LEASE AND SERVICE CONTRACTS. An agreement (the
"ASSIGNMENT AND ASSUMPTION AGREEMENT") evidencing the Seller's assignment and
the Purchaser's assumption of the Lease and any accepted Service Contracts as of
the Closing Date in the form attached hereto and made a part hereof as Exhibit
K.

            8.3 SELLER'S AFFIDAVITS. Such certificates, owner's affidavits and
other evidence signed and delivered by Seller, as may reasonably be required to
induce the title company to issue the Title Policy, without exception except for
the Permitted Exceptions and the liens securing the Existing Indebtedness.

            8.4 FIRPTA AFFIDAVIT. An affidavit certifying that Seller is not a
"FOREIGN PERSON" as that term is defined by Section 1445 of the Code.

            8.5 RESOLUTIONS. Seller's resolutions authorizing the sale
contemplated herein and the execution of this Agreement and all other documents
delivered by Seller at Closing and such other certificates, documents and
instruments as may reasonably be required by the title company to issue the
Title Policy.

            8.6 BILL OF SALE. A bill of sale in the form attached hereto and
made a part hereof as Exhibit L, conveying to Purchaser all Personal Property
and the Intangibles, and all of Seller's right, title and interest, to the
extent assignable, in and to any (i) unexpired warranties and guarantees now in
effect with respect to any part of the Property and/or mechanical equipment and
appliances at the Property, (ii) all architectural, engineering, rezoning and
subdivision plans (if any), specifications, drawings, and reports, and (iii) all
licenses and permits relating to the Property to the extent the same exist and
are assignable.

                                       13
<PAGE>

            8.7 POSSESSION; KEYS. Possession of the Property and keys for the
Improvements in the possession or control of Seller or its agents.

            8.8 ORIGINAL DOCUMENTS. The originals (or copies if originals are
not available) of all the Building Documents.

            8.9 FILES. To the extent available, originals (or copies, if
originals are not available) of all documents and books and records necessary
for the continued operation of the Property, other than proprietary information,
including without limitation, Lease files, rent records, escalation records and
statements and maintenance records.

            8.10 NOTICE OF SALE. Sufficient original letters, executed by
Seller, advising the tenant under the Lease of the sale of the Property to
Purchaser and directing that all rents and other payments thereafter becoming
due be sent to Purchaser or as Purchaser may direct.

            8.11 TERMINATION OF MANAGEMENT AGREEMENT. A termination of
management agreement executed by Seller and its managing agent(s) terminating
any management agreement(s) relating to the Property.

            8.12 TERMINATION OF LEASING AGREEMENT. A termination of leasing
commission agreement executed by Seller and its leasing agent(s) terminating any
leasing agreement(s) relating to the Property, which termination shall set forth
any amounts which Purchaser may be required to pay (with respect to extensions
and renewals) after the Closing, but only to the extent such amounts are
specifically set forth on Exhibit E.

            8.13 GENERAL LEDGERS. Detail general ledgers and trial balances for
the Property, in Excel format, for the fiscal year prior to the Closing Date and
for the interim period from the most recent fiscal year through the Closing
Date.

            8.14 OTHER DOCUMENTS. Any other documents reasonably required by
Purchaser's title company, including but not limited to a Virginia Department of
Taxation Form R-5E and all necessary information for IRS Form 1099-S.

      9. PURCHASER'S CLOSING OBLIGATIONS. Purchaser shall assume or defease the
Existing Indebtedness, and shall pay all other funds required hereunder to be
paid by the Purchaser in connection with the Closing, by federal wire transfer
to the Escrow Agent on the Closing Date. Purchaser shall also execute the
Assignment and Assumption Agreement, and such other documents or instruments as
the Escrow Agent or title company may reasonably require in connection with the
Closing.

      10. SETTLEMENT CHARGES; PRORATIONS AND ADJUSTMENTS.

            10.1 ALLOCATION OF SETTLEMENT CHARGES. Seller shall pay the
Grantor's Tax and the cost of preparation of the Deed in connection with the
Property. Purchaser shall pay the recordation taxes on the Deed, title
examination fees, the title insurance premium, any survey costs, all costs
involved with the assumption of the Existing Indebtedness, including but not
limited to, all assumption fees and costs of Existing Lender's legal fees, all
clerk's and indexing fees and all other settlement expenses except as otherwise
expressly set forth in this Section 10.1. Purchaser and Seller each shall pay
their own legal fees related to the preparation of this Agreement and all
documents required to settle the transaction contemplated hereby.

            10.2 PRORATIONS AND ADJUSTMENTS. At Closing, interest on the
Existing Indebtedness, rents (to the extent prepaid), all real and personal
property taxes, water rents,

                                       14
<PAGE>

sewer charges, electric and other utility charges, operating expenses, any
special assessments, if any, owner's association assessments, and other similar
charges affecting the Property shall be adjusted and prorated as of midnight of
the day prior to the Closing Date, the day of Closing being a day of income and
expense for the Purchaser. Seller shall assign to Purchaser at Closing all of
Seller's right, title and interest in and to reserves, if any, held by the
holder of the Existing Indebtedness as of the Closing Date. Such amount of
reserves will be credited to Seller and paid by Purchaser on the Closing Date.
To the extent practicable, Seller shall attempt to have utility providers read
the meters for the Property on the day prior to Closing for purposes of making
such prorations and adjustments. All other charges or fees customarily prorated
and adjusted in similar transactions shall be adjusted at Closing. All rent
(other than prepaid rent, which shall be paid by Seller to Purchaser) payable by
the tenant of the Property shall be adjusted (prorated) as of the Closing Date
and paid in accordance with the following provisions:

                  a. Base Rent (as defined in the Lease) and Additional Rent (as
defined in the Lease) under the Lease attributable to the month in which the
Closing occurs, shall be adjusted as of the Closing, with Seller being entitled
to the portion thereof attributable to the period of the month immediately
preceding the Closing Date and Purchaser entitled to the balance of such monthly
installment.

                  b. Purchaser shall be entitled to all Base Rent and other sums
due under the Lease to the extent collected on any date after the Closing with
the exception of (a) common area maintenance ("CAM") and real estate tax
reimbursements attributable to periods prior to the Closing; (b) the Base Rent
for the Closing month to which Seller is entitled under (i) above, and (c) to
the extent specified in Subsection c. below, rentals paid by the tenant on
account of rental arrearages for periods preceding the Closing. Annual CAM and
tax reimbursements which are payable by the tenant on an annual basis for the
year of Closing after the conclusion of the calendar year, will be adjusted with
the tenant within ninety (90) days after the expiration of such calendar year
and shall be apportioned between Seller and Purchaser as of the date of Closing,
with Seller being entitled to the portion thereof attributable to the period of
the year immediately preceding the Closing Date and Purchaser being entitled to
the balance of such payment. Purchaser shall pay over to Seller within two (2)
business days following receipt the portion of the installment to which the
Seller is entitled. Additionally, any post-Closing tenant payments of amounts
for special services which were specifically billed by Seller prior to the
Closing Date shall be remitted by Purchaser to Seller within two (2) business
days following Purchaser's receipt thereof.

                  c. Base Rent and Additional Rent which are due, but
uncollected, as of the Closing shall not be adjusted, but Purchaser shall cause
the rent for the period prior to Closing to be remitted to Seller if, as and
when collected, less any reasonable, out-of-pocket expenses incurred by
Purchaser for such collection; provided, that, except with respect to Base Rent
and Additional Rent for the Closing month, which shall be treated as specified
in (i) above, all rents collected subsequent to Closing by Purchaser shall first
be applied to current rentals then due which have accrued subsequent to Closing
and any remaining amounts shall be applied to rental arrearages as of Closing.
Similarly, if Seller receives any Base Rent or other sums under the Lease which
are payable to Purchaser under this Section 10.2, then Seller shall promptly
deliver such sums to Purchaser. Purchaser, at Seller's request, will use
reasonable efforts for six (6) months after the Closing Date to collect past due
rental amounts or other payments owed to

                                       15
<PAGE>

Seller in accordance with this Section 10.2, except that Purchaser has no
obligation to incur any out-of-pocket expenses in the course of such collection
efforts.

                  d. Seller agrees to pay in full as of the Closing Date the
following amounts with respect to the Lease as of the Effective Date: (i) all
leasing commissions and brokerage fees owing in connection with the current
terms of such Lease, (ii) the tenant improvement allowance (if any) due and
payable under such Lease, (iii) the cost of completing any commenced tenant
improvements (if any) even if completion is to occur after Closing, and (iv) to
the extent applicable, any relocation, rent subsidies or other expenses or
incentives offered to the tenant under such Lease in order to satisfy or
terminate the obligations of the tenant to a landlord under another lease.
Purchaser shall be responsible for any commissions, tenant improvements or other
such expenses accruing in connection with leases entered into by Purchaser after
Closing.

All adjustment items to the extent they cannot be precisely determined at
Closing (or to the extent found to be erroneous after the Closing), shall be
estimated at Closing and shall be resolved by the parties in good faith no later
than sixty (60) days after the Closing.

            10.3 RELEASE OF CLOSING ESCROW. Upon receipt of Purchaser's
deliveries required under Section 9 above, and subject to all of Seller's
deliveries having been received and such other conditions to Purchaser's
performance as are contained in Section 6.1 hereof, Escrow Agent shall record
the Deed, disburse the settlement proceeds as indicated on the settlement
statement signed by Purchaser and Seller, and distribute all Closing documents
as directed by counsel for Purchaser and Seller.

      11. CONDEMNATION AND RISK OF LOSS. The risk of condemnation of all or any
portion of the Property or loss or damage to the Property by fire or other
casualty shall be borne by the Seller until Closing. In the event of (a) the
threatened or actual commencement of eminent domain proceedings or actual
condemnation or taking of all or any part of the Property, or (b) damage to the
Property by fire or other casualty, act of God or any other event on or prior to
the Closing Date, which would cost in excess of Four Hundred Thousand Dollars
($400,000.00) to repair or cause a material loss in the income generated by such
Property, Purchaser, at its sole option exercisable within thirty (30) days
following receipt of written notice of the event giving rise to the exercise of
such option, shall have the right to terminate this Agreement, in which event
the Deposit shall be returned to Purchaser, and neither party shall have any
further obligations or liabilities to the other, subject to the obligations of
the Purchaser under Section 5 above. In the event of a casualty which does not
fall within (b) above, then the Closing shall occur as provided herein.
Purchaser understands and agrees that if it does not exercise its termination
option in the event of condemnation or casualty as described in (a) or (b)
above, or if Purchaser is required to proceed to Closing pursuant to the
immediately preceding sentence, the terms and conditions of the documents
governing the Existing Indebtedness will control the use of any insurance
proceeds and the settlement of any insurance claims related thereto with respect
to the Property, and that Purchaser will have no rights with respect to such
proceeds or claims. Notwithstanding the foregoing, in such an event, Seller
shall assign all of its rights to applicable insurance or condemnation proceeds,
as applicable, to Purchaser and the Purchase Price shall be reduced by the
amount of any deductible under such insurance policy. The provisions of this
Section 11 shall expressly survive Closing and delivery of the Deed for the
Property.

      12. DEFAULT PROVISIONS; REMEDIES.

                                       16
<PAGE>

            12.1 PURCHASER'S DEFAULT. If Purchaser fails to consummate the
purchase contemplated herein after all conditions precedent to Purchaser's
obligation to consummate the transactions herein contemplated have been
satisfied or waived by Purchaser, and Seller is not in default hereunder, and
Seller has notified Purchaser of such default and Purchaser has failed to cure
such default within ten (10) days of Seller's written notice, then Escrow Agent
shall deliver to Seller the Deposit. In such event, the Deposit shall be deemed
as full and complete liquidated damages and the sole and exclusive remedy of
Seller, the parties hereby agreeing that they have considered carefully the loss
to Seller that would be a consequence of such default and that the Deposit is a
reasonable estimate of such loss. Upon payment to Seller of the Deposit, this
Agreement shall terminate, and neither party shall have any further obligations
or liabilities to any other party, other than any obligations or liabilities
which expressly survive any termination of this Agreement.

            12.2 SELLER'S DEFAULT. Except as otherwise provided herein, if
Seller breaches its representations, warranties, covenants and/or agreements
hereunder or fails to consummate the sale contemplated herein by the Closing
Date after all conditions precedent to Seller's obligations hereunder have been
satisfied or waived by Purchaser and provided that Purchaser is not in default
hereunder, and Purchaser has notified Seller of such default and Seller has
failed to cure such default within ten (10) days of Purchaser's written notice
then, except as otherwise provided herein, Purchaser shall be entitled, at its
option, to notify Seller of the election by Purchaser to terminate this
Agreement, whereupon Escrow Agent shall return the Deposit to Purchaser, Seller
shall reimburse Purchaser for its Pursuit Costs in connection with the
transactions contemplated by this Agreement (including but not limited to
reasonable attorneys' and consultants' fees) up to a maximum aggregate amount
equal to Forty Thousand Dollars ($40,000.00), such costs to be included in
Purchaser's written notice accompanied by reasonable documentation evidencing
such Pursuit Costs, and neither party will have any further obligation to the
other hereunder, other than the obligations of the Purchaser under Section 5.
Alternatively, in the event the Seller shall fail to close as required
hereunder, Purchaser, at its election, shall be entitled to bring suit for
specific performance, inasmuch as the parties recognize and acknowledge that the
Property owned by Seller is unique, and that there is no adequate remedy at law
to compensate fully Purchaser for a breach by Seller of Seller's obligations to
convey the Property of the Seller to Purchaser in accordance with the terms and
conditions of this Agreement. Except as otherwise specifically provided for
under this Section 12.2, in no event shall Purchaser be entitled to monetary
damages for a default by Seller to close hereunder.

      13. OBLIGATIONS OF SELLER PENDING CLOSING. Between the date hereof and the
Closing Date, Seller agrees:

            13.1 OCCUPANCY AT CLOSING. The parties understand that the Property
will be delivered subject only to the rights of the tenant under the Lease and
rights of parties under the Service Contracts assumed by Purchaser, Permitted
Exceptions and the Existing Indebtedness.

            13.2 LEASING. Seller agrees that it will not enter into any new
leases for premises in the Property or extend, modify or terminate the existing
Lease without the Purchaser's consent, which consent shall not be unreasonably
delayed, withheld or conditioned (except that Purchaser shall have no obligation
to consent to any termination of the Lease under any circumstance).

                                       17
<PAGE>

            13.3 MAINTENANCE AND OPERATION OF PROPERTY. Seller shall continue to
maintain the Property consistent with its prior practices, in order that its
present operating condition be maintained, normal wear and tear excepted, and
shall cause the continuation of the normal operation thereof, including the
purchase and replacement of supplies and equipment. Seller shall not remove or
permit to be removed from the Property any Personalty, except as may be
necessary for repairs or discarding worn out or useless items, provided that
discarded items shall be replaced with new items of substantially equal quality
and quantity and shall be free and clear of any lien or encumbrance.

            13.4 NO ACTION. Seller shall not knowingly take any action or
direct, require or advise any other person or entity to take any action that
would invalidate, void or make untrue any representation or warranty provided
under this Agreement or otherwise breach this Agreement.

            13.5 ADDITIONAL DELIVERIES. Seller shall deliver to Purchaser
promptly following its receipt copies of any notices received by Seller or its
management agent from the holder of any liens existing against the Property or
the tenants pertaining to the Property from and after the date hereof through
Closing.

            13.6 SCHEDULED PAYMENTS OF THE EXISTING INDEBTEDNESS. Seller will
make the scheduled monthly payments of principal and interest under the Existing
Indebtedness until Closing and shall not take any action or fail to take any
action which would constitute a default under the Existing Indebtedness.

      14. MISCELLANEOUS PROVISIONS.

            14.1 COMPLETENESS AND MODIFICATION. This Agreement constitutes the
entire agreement between the parties hereto with respect to the transactions
contemplated herein, and it supersedes all prior discussions, understandings or
agreements between the parties. This Agreement shall not be modified or amended
except by an instrument or writing signed by and on behalf of the parties.

            14.2 ADDITIONAL DOCUMENTS. Purchaser and Seller agree that they
will, within six (6) months after the Closing, duly execute and deliver to each
other any additional conveyances, assignments, documents and instruments, and
shall take or cause to be taken such further actions (including the making of
filings), which are necessary in connection with the consummation of the
acquisition and contribution contemplated herein.

            14.3 SEVERABILITY. If fulfillment of any provision of this
Agreement, or performance of any transaction related hereto, at the time such
fulfillment or performance shall be due, shall involve transcending the limit of
validity prescribed by law, then the obligation to be fulfilled or performed
shall be reduced to the limit of such validity; and if any clause or provision
contained in this Agreement operates or would prospectively operate to
invalidate this Agreement in whole or in part, then such clause or provision
only shall be held ineffective, as though not herein contained, and the
remainder of this Agreement shall remain operative and in full force and effect.

            14.4 CUMULATIVE REMEDIES. Except as specifically provided in this
Agreement, each and every of the rights, benefits, and remedies provided to
Purchaser or Seller by this Agreement, or any instruments or documents executed
pursuant to this Agreement, are

                                       18
<PAGE>

cumulative and shall not be exclusive of any other rights, remedies and benefits
allowed to such party by this Agreement, at law or in equity.

            14.5 CONSTRUCTION. Each party hereto hereby acknowledges that all
parties hereto participated equally in the negotiation and drafting of this
Agreement and that, accordingly, no court construing this Agreement shall
construe it more stringently against one party than against the other.

            14.6 PRONOUNS. All pronouns and any variations thereof shall be
deemed to refer to the masculine, feminine, neuter, singular or plural, as the
identity of the person or entity may require.

            14.7 BINDING EFFECT; ASSIGNMENT. This Agreement shall be binding
upon and inure to the benefit of the parties hereto, and their respective
successors and permitted assigns. Purchaser may not assign this Agreement
without the prior written consent of Seller, which consent shall not be
unreasonably withheld, conditioned or delayed; provided, however, that Purchaser
shall have the right to assign this Agreement (or any portion hereof) to one or
more subsidiaries or affiliates of Purchaser without Seller's consent, so long
as Purchaser has direct or indirect control or management of any such assignee.
Seller shall not assign this Agreement.

            14.8 WAIVER; MODIFICATION. Failure by Purchaser or Seller to insist
upon or enforce any of its rights hereto shall not constitute a waiver thereof.

            14.9 GOVERNING LAW. This Agreement shall be governed by and
construed under the laws of the Commonwealth of Virginia.

            14.10 HEADINGS. The headings are used herein for convenience of
reference only, and shall not be deemed to vary the content of this Agreement.

            14.11 EXHIBITS. All Exhibits attached hereto are incorporated herein
and made a part of this Agreement.

            14.12 COUNTERPARTS. To facilitate execution, this Agreement may be
executed in as many counterparts as may be required; and it shall not be
necessary that the signature of each party, or that the signatures of all
persons required to bind any party, appear on each counterpart; but it shall be
sufficient that the signature of each party or that the signatures of the
persons required to bind any party, appear on one or more such counterparts. All
counterparts shall collectively constitute a single agreement. This document and
any amendment hereto may be executed by facsimile and any such facsimile shall
be deemed to constitute an original for all purposes hereof.

            14.13 NOTICES. All notices, requests, consents, and other
communications hereunder shall be in writing and shall be personally delivered,
sent by facsimile transmission, sent by Federal Express or other recognized
overnight delivery service, prepaid by the party sending such notice, to the
addresses indicated below.

            IF INTENDED FOR SELLER TO:
                  Armada/Hoffler Investment Properties, L.P.
                  222 Central Park Avenue
                  Suite 2100
                  Virginia Beach, Virginia 23462
                  Fax No.: (757) 424-2513

                                       19
<PAGE>

                  Attention: Shelly R. Hampton

            WITH A COPY TO:
                  Faggert & Frieden, P.C.
                  222 Central Park Avenue, Suite 1300
                  Virginia Beach, Virginia 23462
                  Fax No.:  (757) 424-0102
                  Attention: David Y. Faggert

            IF INTENDED FOR PURCHASER TO:
                  Columbia Equity Trust, Inc.
                  1750 H Street, NW, Suite 500
                  Washington, D.C. 20006
                  Fax No.:  (202) 303-3088
                  Attention:  Clinton D. Fisch

            WITH A COPY TO:
                  Watt, Tieder, Hoffar & Fitzgerald LLP
                  8405 Greensboro Drive, Suite 100
                  McLean, Virginia 22102
                  Fax No. (703) 749-0479
                  Attention: Colin J. Smith, Esq.

      The addresses and parties set forth above may be changed from time to time
by any party by notice to the other. For purposes of this Agreement, notices
shall be effective upon receipt or refusal thereof.

            14.14 SECTION 1031 EXCHANGE. Upon request of either party made not
later than five (5) business days prior to Closing, Purchaser and Seller agree
to reasonably cooperate with the other (at the requesting party's sole cost and
expense) in structuring the purchase and sale of the Property as contemplated by
this Agreement as part of a like-kind exchange pursuant to Section 1031 of the
Code. The requesting party shall indemnify the other party against all costs
associated with the like-kind exchange process. The like-kind exchange shall not
reduce, diminish or adversely affect the parties' rights or remedies under this
Agreement in any respect, nor shall the consummation of the exchange cause any
delay in the Closing.

            14.15 BUSINESS DAY. As used herein, the term "BUSINESS DAY" shall
mean any day other than a Saturday or Sunday, or other day recognized as a
holiday by the U.S. Government.

            14.16 SURVIVAL. It is the express intention and agreement of the
parties hereto that the covenants, agreements, statements, representations,
warranties and indemnities made in this Agreement by the respective parties
shall survive the execution and delivery of the Deed at Closing for twelve (12)
months following Closing.

            14.17 ATTORNEYS' FEES. If any party institutes any proceeding or
action to obtain enforce this Agreement against another party, the party which
substantially prevails in such proceeding or action, as determined by the
trier-of-fact, shall be entitled to be reimbursed by the non-prevailing party
for reasonable, out-of-pocket costs and other expenses, including reasonable

                                       20
<PAGE>

attorneys' fees, incurred by the substantially prevailing party in connection
with such proceeding or action.

            14.18 WAIVER OF JURY. SELLER AND PURCHASER EACH HEREBY IRREVOCABLY
WAIVES TRIAL BY JURY IN ANY ACTION OR PROCEEDING BROUGHT BY OR AGAINST THE OTHER
PARTY UNDER OR IN CONNECTION WITH THIS AGREEMENT.

            14.19 BROKERAGE COMMISSION. Seller and Purchaser represent and
warrant to each other that they have dealt with no brokers or finders in
connection with the sale of the Property other than Cushman and Wakefield (the
"BROKER") and that no brokerage fee or real estate commission is or shall be due
or owing in connection with this transaction other than to the Broker, who shall
be paid solely by Seller in accordance with the terms of a separate written
agreement. Seller and Purchaser hereby indemnify and hold the other harmless
from any and all loss, costs or damage (including, without limitation,
reasonable attorneys fees and expenses) arising out of any claims of any broker
or agent so claiming based on action or alleged action of the indemnifying party
recognizing the Seller alone shall bear the cost of the Broker as aforesaid.
This Section 14.19 shall survive Closing.

            14.20 CONFIDENTIALITY. All surveys, tests, studies, inspections and
investigations conducted by Purchaser under this Agreement, all documents, books
and records provided by Seller to Purchaser under this Agreement, including
without limitation the Building Documents and the Lease, and all terms of this
Agreement will be treated by Purchaser as confidential information, and
Purchaser will not disclose the same to any other person other than its
attorneys, accountants, prospective lenders, mortgage bankers, financial
advisors or investors, and any architects, engineers or consultants specifically
retained by Purchaser in connection with its acquisition of the Property. It is
understood by Seller that Purchaser may be required to disclose certain details
of this transaction in order to comply with Securities and Exchange Commission
guidelines which may be applicable to Purchaser as a public real estate
investment trust. Purchaser will advise all such attorneys, accountants,
prospective lenders, mortgage bankers, financial advisors and investors,
architects, engineers and consultants of the confidential nature of such
information, and will instruct each such person to maintain confidentiality. All
documents, books and records provided by Purchaser to Seller under this
Agreement and all terms of this Agreement will be treated by Seller as
confidential information, and Seller will not disclose the same to any person
other than its attorneys. Both parties' obligations under this Section 14.20
will survive any termination of this Agreement.

            14.21 STANDSTILL PERIOD. Until Closing or the earlier termination of
this Agreement by either party, Seller agrees that it will not, directly or
indirectly, offer to sell, or solicit any offers to purchase or negotiate for
the sale or disposal of the Property with any other party other than Purchaser.

            14.22 EFFECTIVE DATE. THE "EFFECTIVE DATE" SHALL BE THE DATE
UPON WHICH BOTH SELLER AND PURCHASER HAVE EXECUTED THIS AGREEMENT AND AN
ORIGINAL THEREOF HAS BEEN DELIVERED TO EACH.

[THE BALANCE OF THIS PAGE HAS BEEN LEFT BLANK INTENTIONALLY]

                                       21
<PAGE>

IN WITNESS WHEREOF, the parties hereto have executed this Agreement under seal
as of the day and year first above written.

                              PURCHASER:

                              COLUMBIA EQUITY TRUST, INC., a Maryland
                              corporation

                              By: /s/ Clinton Fisch
                                  ----------------------------------------------
                              Name: Clinton Fisch
                              Title: SVP

                              SELLER:

                              ARMADA/HOFFLER INVESTMENT PROPERTIES, L.P.

                              By: AGLF, INC., its General Partner

                              By: /s/ Louis S. Haddad
                                  ----------------------------------------------
                                  Louis S. Haddad, Vice President

                              ESCROW AGENT:

                              COMMERCIAL TITLE GROUP, INC.

                              By: /s/ Douglas Nichols
                                  ----------------------------------------------
                              Name: Douglas Nichols
                              Title: President

                                LIST OF EXHIBITS

<TABLE>
<S>                 <C>
EXHIBIT A           Legal Description - Property
EXHIBIT B           Schedule of Personal Property
EXHIBIT C           Description of Existing Indebtedness
EXHIBIT D           Chubb Waiver Letter
EXHIBIT E           Schedule of Lease, Security Deposits, Commissions, Tenant
                    Improvements
EXHIBIT F           Schedule of Service Contracts
EXHIBIT G           Form of Tenant Estoppel Certificate
EXHIBIT H-1         Form of CC&R Estoppel Certificate (Ingress-Egress Easement)
EXHIBIT H-2         Form of CC&R Estoppel Certificate (Declaration)
EXHIBIT I           Form of Guarantor Estoppel Certificate
EXHIBIT J           Form of Deed
EXHIBIT K           Form of Assignment and Assumption of Lease and Contracts
EXHIBIT L           Form of Bill of Sale
EXHIBIT M           Property Information
</TABLE>

                                       22
<PAGE>

                                    EXHIBIT A
                          LEGAL DESCRIPTION - PROPERTY

ALL THOSE CERTAIN lots, pieces or parcels of land, situate, lying and being in
Fairfax County, Virginia, and more particularly described as follows:

All of that certain lot, piece or parcel of land known as Parcel 10A-1, Lake
Fairfax Business Center, as shown on that certain plat entitled "PLAT SHOWING
MINOR LOT LINE ADJUSTMENT OF PARCELS 9 AND 10A LAKE FAIRFAX BUSINESS CENTER
HUNTER MILL DISTRICT FAIRFAX COUNTY, VIRGINIA", dated January 29, 1999, which
plat is attached to instrument recorded in Deed Book 10916 at Page 469, among
the land records of Fairfax County, Virginia, and being more particularly
described by metes and bounds as follows:

Beginning at an iron pipe found on the southeasterly line of Parcel 7A, Lake
Fairfax Business Center marking the northwesterly corner of Parcel 8, Lake
Fairfax Business Center; thence with the westerly line of said Parcel 8, Lake
Fairfax Business Center

S 12 degrees 44' 54" E, 106.60 feet

To an iron pipe set marking the most northerly corner of Parcel 9A, Lake Fairfax
Business Center;

Thence with the northwesterly line of said Parcel 9A, Lake Fairfax Business
Center;

S 47 degrees 02' 27" W, 320.90 feet

To an iron pipe set on the northeasterly line of Outlot D, Reston, Section 909
marking the most westerly corner of Parcel 9A, Lake Fairfax Business Center;

Thence with said northeasterly line of Outlot D, Reston, Section 909 and
continuing with the northeasterly lines of Outlot E and Outlot F, Reston,
Section 909

N 42 degrees 58' 28" W, 580.18 feet

To an iron pipe set on the southeasterly corner of Outlot 8A, Reston, Section
909 and marking the northeasterly corner of said Outlot F, Reston, Section 909;

Thence with the northeasterly line of said Outlot 8A, Reston, Section 909

N 42 degrees 57' 01" W, 134.16 feet

To an iron pipe set marking the most southerly corner of Parcel 18B, Lake
Fairfax Business Center;

Thence with the southeasterly lines of Parcel 18B, Lake Fairfax Business Center;

N 47 degrees 02' 59" E, 182.60 feet to an iron pipe set and

N 41 degrees 05' 46" E, 179.37 feet

To an iron pipe set on the southwesterly line of aforementioned Parcel 7A, Lake
Fairfax Business Center marking the southeasterly corner of said Parcel 18B,
Lake Fairfax Business Center;

Thence with the southwesterly and southeasterly lines of said Parcel 7A, Lake
Fairfax Business Center the following eight (8) courses:

S 31 degrees 54' 10" E, 549.42 feet to an iron pipe set;

<PAGE>

S 58 degrees 05' 50" W, 75.01 feet to an iron pipe set;

S 31 degrees 54' 10" E, 36.00 feet to an iron pipe set;

S 42 degrees 05' 39" E, 45.21 feet to an iron pipe set;

S 31 degrees 54' 10" E, 50.00 feet to an iron pipe set;

N 58 degrees 05' 50" E, 85.51 feet to an iron pipe set;

N 31 degrees 54'10" W, 56.83 feet to an iron pipe set and

N 59 degrees 38' 08" E, 117.84 feet to the point of beginning.

Containing 209,973 square feet or 4.82032 acres of land, more or less.

TOGETHER WITH AND SUBJECT TO the rights, benefits, burdens and obligations
created by that certain Ingress-Egress Easement and Maintenance Agreement dated
February 26, 1999 and recorded on April 30, 1999 in Deed Book 10896 at Page
1139, among the Land Records of Fairfax County, Virginia.

AND BEING the same property conveyed to Armada/Hoffler Investment Properties,
L.P., a Virginia limited partnership by Deed from The Advance Group/Lake
Fairfax, LLC, a Virginia limited liability company dated as of November 17, 2000
and recorded December 12, 2000 among the land records of Fairfax County,
Virginia in Deed Book 11632 at page 1125.

                               EXHIBIT A, PAGE 2
<PAGE>

                                    EXHIBIT B
                          SCHEDULE OF PERSONAL PROPERTY

                                      NONE

<PAGE>

                                    EXHIBIT C
                      DESCRIPTION OF EXISTING INDEBTEDNESS

1.    PROMISSORY NOTE

2.    DEED OF TRUST, ASSIGNMENT OF LEASES AND RENTS AND SECURITY AGREEMENT
      RECORDED IN BOOK 10955, PAGE 1545 IN THE CLERK'S OFFICE

3.    LOAN AGREEMENT

4.    ENVIRONMENTAL INDEMNIFICATION AGREEMENT

5.    UCC-1 FINANCING STATEMENT FILED WITH THE CLERK'S OFFICE AS FILE NO.
      99-6308

6.    UCC-1 FINANCING STATEMENT FILED WITH THE CHESAPEAK CLERK'S OFFICE AS FILE
      NO. 62847

7.    UCC-1 FINANCING STATEMENT FILED WITH THE SCC AS FILE NO. 9906117002

8.    ASSIGNMENT OF DEED OF TRUST, DATED SEPTEMBER 20, 2000 RECORDED IN DEED
      BOOK 11633, AT PAGE 380 IN THE CLERK'S OFFICE F FAIRFAX COUNTY (THE
      "FAIRFAX CLERK'S OFFICE")

9.    CONSENT AND ASSUMPTION AGREEMENT WITH RELEASE RECORDED IN DEED BOOK 11633,
      AT PAGE 385 IN THE CLERK'S OFFICE

10.   ENVIRONMENTAL AND HAZARDOUS SUBSTANCE INDEMNITY AGREEMENT

11.   UCC 1 FINANCING STATEMENT, BEING FILE NO. 00-013046, IN THE CLERK'S OFFICE

12.   UCC AMENDMENT TO FINANCING STATEMENT, BEING FILE NO. 00-013047, IN THE
      CLERK'S OFFICE

13.   UCC AMENDED FINANCING STATEMENT RECORDED AS INSTRUMENT NO. 062847 IN THE
      CLERK'S OFFICE, CITY OF CHESAPEAKE

14.   UCC FINANCING STATEMENT RECORDED AS INSTRUMENT NO. 065763 IN THE CITY OF
      CHESAPEAKE, CLERK'S OFFICE

<PAGE>

15.   UCC FINANCING STATEMENT FILED WITH THE SCC AS INSTRUMENT NO. 00-12-13-7007

16.   UCC FINANCING STATEMENT AMENDMENT FILED WITH THE SCC AS INSTRUMENT NO.
      01-01-08-7016

                               EXHIBIT A, PAGE 2
<PAGE>

                                    EXHIBIT E
     SCHEDULE OF LEASES, SECURITY DEPOSITS, COMMISSIONS, TENANT IMPROVEMENTS

                  1. Schedule of Leases.

Deed of Lease, dated effective as of September 15, 1998, between The Advance
Group/Lake Fairfax, L.L.C. (the "Original Landlord") and Chubb Computer
Services, Inc. ("Tenant"), as modified by an Agreement, dated April 28, 1999,
between Original Landlord, Tenant and Armada/Hoffler Construction Company, and
as amended pursuant to a First Amendment to Lease Agreement, dated effective as
of May 4, 1999, and a Second Amendment to Lease Agreement, dated February 7,
2000, and a Guaranty of Lease, made as of September 15, 1998, made by Federal
Insurance Company in favor of the Original Landlord.

2.    Security Deposit. - None

3.    Commissions - None

4.    Tenant Improvements - None<PAGE>

                                                                    EXHIBIT 10.8

                         AGREEMENT OF PURCHASE AND SALE

     THIS AGREEMENT OF PURCHASE AND SALE (hereinafter referred to as the
"Agreement"), made this 25th day of April, 2006, by and between FOULGER LAND
LIMITED PARTNERSHIP, a Virginia limited partnership ("FLLP"), ARGO ORCHARD RIDGE
MANAGER, INC., a Maryland corporation and ARGO INVESTMENT COMPANY, LC, a
Maryland limited liability company (the "Argo Sellers") (FLLP and the Argo
Sellers are sometimes herein collectively herein referred to as "Seller") and
COLUMBIA EQUITY TRUST, INC., a Maryland corporation (hereinafter referred to as
"Purchaser").

                                    RECITALS:

     R.1. The Argo Sellers are the sole members of Argo Orchard Ridge, LLC, a
Maryland limited liability company ("Argo"), and own one hundred percent (100%)
of the limited liability company membership interests (the "Argo Membership
Interests") in Argo.

     R.4. FLLP and Argo (collectively herein referred to as "Owner"), as tenants
in common, pursuant to the terms of that certain Tenants-in-Common Agreement,
dated (the "TIC Agreement") own certain real property located in Gaithersburg,
Montgomery County, Maryland, having an address of 101 Orchard Ridge Drive,
Gaithersburg, Maryland, and as more particularly described on EXHIBIT A attached
hereto; together with all right, title and interest of Seller in and to all
easements, rights, privileges, rights-of-way, hereditaments, tenements and
appurtenances belonging to the land, all right, title and interest in and to all
open or proposed highways, streets, roads, avenues, alleys, easements, strips,
gores and rights of way, in, on, across, in front of, contiguous to, abutting or
adjoining the land (hereinafter collectively with the land referred to as the
"Real Property"), and together with all improvements situate thereon, including
an approximately 102,396 square foot office building and all appurtenances owned
by Seller and applicable thereto (the "Improvements").

     R.5. Owner also owns certain personal property used or useable in
conjunction with the Real Property and Improvements, including all personal
property located on or at the Real Property or Improvements as of the date
hereof (provided the same is not owned by tenants occupying space in the
Improvements pursuant to the leases as hereafter defined), including that
personal property as more particularly described on EXHIBIT B attached hereto
and made a part hereof (hereinafter referred to as the "Personal Property").

     R.6. Owner also owns certain intangible property used or useable in
connection with the Real Property, Improvements and Personal Property,
including, but not limited to, Owner's rights in and to certain trade names,
licenses, permits, authorizations and goodwill used in connection with any part
of the Real Property and Improvements; Owner's rights in and to all leases,
subleases, and other rental agreements which grant a possessory interest in and
to any space in the Improvements, including the Leases; Owner's interest, if
any, in and to any and all licenses, permits, guarantees and warranties now in
effect with respect to the Real Property,

<PAGE>

Improvement and Personal Property; all written or oral contracts or agreements
binding on Owner or the Property (all such contracts in effect as of the date
hereof being described on EXHIBIT C attached hereto and made a part hereof and
being hereinafter collectively referred to as the "Contracts") in effect at
Settlement (as hereafter defined) in any way relating to the Real Property; and
all prepaid rents, security, damage, lease and/or other deposits established in
connection with the Property and currently held by Owner (collectively, the
"Intangible and Other Property") (the Real Property, Improvements, Personal
Property, Contracts, Leases (as such leases are identified on EXHIBIT D attached
hereto and made a part hereof, the "Leases"), and Intangible and Other Property
are sometimes collectively referred to herein as the "Property").

     R.7. Purchaser desires to purchase from Seller and Seller desires to sell
to Purchaser, the FLLP Membership Interests (as hereafter defined) and the Argo
Membership Interests, in accordance with the terms and conditions hereinafter
set forth.

     NOW, THEREFORE, in consideration of the mutual promises of the parties
hereto, made one to another, and for other good and valuable consideration, the
receipt and sufficiency of which is hereby acknowledged, the parties hereto
agree as follows:

     1. Agreement of Purchase and Sale. Seller hereby agrees to sell and convey
the FLLP Membership Interests (as herein defined) and the Argo Membership
Interests to Purchaser, and Purchaser hereby agrees to purchase the FLLP
Membership Interests and the Argo Membership Interests from Seller, in
accordance with the terms and provisions hereof.

     2. Title and Survey. At Settlement, Argo and the LLC shall hold marketable
fee simple title to the Property of record and in fact, which shall be insurable
at standard rates by Commonwealth Land Title Insurance Company (the "Title
Insurer"), excepting only the following permitted exceptions (the "Permitted
Exceptions"):

          A. The lien of real estate taxes not yet due and payable;

          B. All applicable codes, regulations, ordinances and other
restrictions of any governmental or quasi-governmental authority (including any
zoning authority) having jurisdiction over the Property; and

          C. Such other matters as are set forth on Purchaser's Title Commitment
and Survey to which Purchaser does not object as hereinafter set forth.

     Prior to the expiration of the Feasibility Study Period (as hereafter
defined), Purchaser shall (i) cause the Title Insurer to cause title to the
Property to be inspected and to issue to Purchaser a commitment for title
insurance (the "Title Commitment"), together with all documents referred to in
the Title Commitment, including without limitation, deeds, lien instruments,
plats, restrictions, easements, UCC financing statement searches, and judgment
searches (collectively, the "Title Documents"), and (ii) at its option, cause a
licensed surveyor to prepare a current ALTA survey of the Property (the
"Survey"). In the event the Title Commitment or Survey discloses encumbrances on
title to the Property which are unacceptable to Purchaser, Purchaser shall give
notice thereof (in accordance with the terms hereof) to Seller not later than
five (5) days prior to the expiration of the Feasibility Study Period (which
notice

                                       2

<PAGE>

shall enclose a copy of the Title Commitment, Title Documents and Survey)
specifying the objections of Purchaser (the "Title Objections"). Seller shall
have the option, but not the obligation, exercised by notice to Purchaser not
later than the business day immediately preceding the expiration of the
Feasibility Study Period, to cure the Title Objections (or any of them) at
Seller's own expense to the reasonable satisfaction of Purchaser, or not to cure
one or more Title Objections. A failure of Seller to timely give such notice
shall be deemed Seller's election not to cure any Title Objections. In the event
Seller elects to cure the Title Objections, the time specified for Settlement
shall be extended for the period necessary for such cure, not to exceed thirty
(30) days. If Seller elects not to cure all Title Objections, then (i) the
Deposit (as hereafter defined) shall be returned to Purchaser, and (ii) this
Agreement shall be null and void, and neither party shall have any further
right, liability or obligation hereunder except for Purchaser's indemnification
obligation pursuant to Section 9 hereof which shall survive any such
termination; provided, however, that Purchaser may elect, by written notice to
Seller given not later than the earlier of five (5) business days of receipt of
Seller's notice (or deemed notice) of its election not to cure all Title
Objections, or the final day of the Feasibility Study Period, to waive such of
the Title Objections as Seller has elected not to cure, in which event the
parties shall proceed with Settlement in accordance with the terms hereof
(provided that the foregoing cure period shall remain applicable to any Title
Objections which Seller has elected to attempt to cure), with no abatement in
the Purchase Price. In the event Purchaser does not terminate this Agreement in
accordance with Section 9 hereof, the same shall be deemed Purchaser's election
to waive such Title Objections. In the event Seller elects to cure some or all
Title Objections, but has been unable to effectuate such cure to the reasonable
satisfaction of Purchaser by that date which is thirty (30) days after the date
otherwise set forth for Settlement, then Purchaser shall have the right, within
five (5) business days after such thirty (30) day period, to (i) waive the
uncured Title Objections and proceed to Settlement in accordance with the terms
hereof, with no abatement in the Purchase Price, or (ii) to terminate this
Agreement, upon which the Deposit shall be returned to Purchaser and neither
party shall have any further right or liability hereunder, other than those
obligations which expressly survive the termination of this Agreement. The
foregoing notwithstanding, Seller shall remove or cause to be removed, at or
prior to Settlement hereunder, any monetary lien created by or at the direction
of Seller.

     3. Purchase Price. The purchase price ("Purchase Price") for the FLLP
Membership Interests and the Argo Membership Interests is Twenty Seven Million
Four Hundred Forty Thousand Dollars ($27,440,000.00), which shall be as set
forth below.

     The Purchase Price shall be paid by (i) assumption by Purchaser of Owner's
outstanding debt on the Property as discussed below, and (ii) delivery by
Purchaser to Seller of the balance of the Purchase Price which shall be paid by
federal wire transfer of immediately available funds to be received by Seller
not later than 2:00 p.m. Eastern Time on the Settlement Date.

     The debt to which the Property is currently subject is that certain loan
(the "Loan") extended by UBS Real Estate Investments, Inc. ("UBS"), originally
in the principal amount of $15,500,000.00. Purchaser shall promptly make
application to UBS and diligently pursue in good faith, approval of the
transactions contemplated by this Agreement. Seller shall be solely responsible
for the payment of the assumption/transfer fee to UBS, as well as any and all
other fees and expenses charged by or on behalf of UBS (including attorneys'
fees) in connection with such assumption (or attempted assumption). Purchaser
shall diligently and in good faith

                                       3

<PAGE>

cooperate with Seller and UBS in connection with obtaining UBS' approval of the
transactions contemplated by this Agreement, including, but not limited to,
promptly supplying all information requested by UBS, financial or otherwise,
necessary therefor, and providing to UBS an acceptable substitute non-recourse
carveout guarantor(s) in the place and stead of those originally set forth in
the Loan. It shall be a condition precedent to Seller's and Purchaser's
obligation to consummate Settlement hereunder that UBS approve the transactions
contemplated by this Agreement, including the Owner entering into the Nextone
Lease (as hereinafter defined) and the Harvey Cleary Lease (as hereinafter
defined) and the associated buy-out of the Heller Ehrman lease (collectively,
the "Lease Transactions"). In the event UBS does not, despite Purchaser's good
faith efforts, approve the transactions contemplated by this Agreement, this
Agreement shall terminate, the Deposit shall be returned to Purchaser and
neither party shall thereafter have any further right or obligation hereunder
other than Purchaser's indemnification obligations hereunder which shall survive
such termination.

     4. Deposit.

          A. Simultaneously with the execution hereof by all parties hereto,
Purchaser shall deliver to the Title Insurer, as escrow agent, an initial
deposit of Seven Hundred Fifty Thousand Dollars ($750,000.00) (the "Initial
Deposit"). Upon the expiration of the Feasibility Study Period, provided
Purchaser has not timely terminated this Agreement, Purchaser shall deliver to
the Title Insurer an additional deposit in the amount of Two Hundred Fifty
Thousand Dollars ($250,000.00) (the "Additional Deposit"). As used herein the
term "Deposit" shall mean the Initial Deposit, the Additional Deposit, and all
accrued interest in the Escrow Account. The Deposit shall be held in escrow by
the Title Insurer in an interest-bearing escrow account (the "Escrow Account")
accruing to the benefit of the party entitled to the Deposit in accordance with
the provisions hereof, such escrow account to be maintained at a federally
insured financial institution. All interest earned on the escrow account shall
be charged to the account of Purchaser for federal income tax purposes, and, in
connection therewith, Purchaser represents that its federal taxpayer
identification number is 20-1978579.

          B. The Title Insurer shall deliver the Deposit held hereunder (a) to
or at the direction of Purchaser concurrent with the Settlement, provided
Purchaser shall pay the full Purchase Price to Seller (or at Purchaser's
direction to be applied against the Purchase Price at Settlement), or (b) at
such other time, before or after Settlement, to Purchaser or Seller, as such
party becomes entitled to the Deposit as provided in this Agreement.

          C. If this escrow shall be involved in any litigation or controversy,
the parties hereto shall severally hold the Title Insurer free and harmless
against any cost or expense that may be suffered by it by reason of such
litigation or controversy, other than due to its negligence or malfeasance. All
such costs and expenses shall be paid by the party who does not prevail in such
litigation. In addition, the party who prevails shall be indemnified against any
cost or expense, including reasonable attorneys' fees (both at trial and on
appeal), and replacement of any depletion in the escrow funds, if such funds are
ultimately to be paid to the prevailing party.

          D. In the event conflicting demands are made, or notices served, upon
the Title Insurer with respect to this escrow, the Title Insurer shall have,
without limitation, the following rights and obligations:

                                       4

<PAGE>

               (i) Withhold and stop all further proceedings in, and performance
of this escrow for a reasonable period of time to permit resolution; or

               (ii) File a suit in interpleader and obtain an order from a court
of competent jurisdiction requiring the parties to interplead and litigate in
such court their several claims and rights amongst themselves. In the event such
interpleader suit is brought, and the escrow funds paid and/or delivered into
court, the Title Insurer shall ipso facto be fully released and discharged from
all obligations to perform any and all duties or obligations relative to such
funds which are imposed upon it by this Agreement.

          E. The Title Insurer, in its capacity as escrow agent, is not to be
held liable for the sufficiency or correctness of the form, manner of execution
or validity of any instrument that might be deposited into the escrow, nor as to
the identity, authority or rights of any person executing the same, nor the
failure of any other party to comply with any provisions of any agreement,
contract or other instrument filed herein, and its duties hereunder shall be
limited to the safekeeping of the money, instruments, or other documents
received by it, and for the disposition of the same in accordance with the
provisions of this Agreement, and for the discharge of its obligations specified
in this Agreement.

          F. Prior to the earlier of the Settlement or the termination of this
Agreement in accordance with its terms, neither party shall have the right to
withdraw any instruments or monies deposited by them with the Title Insurer,
except as herein specifically provided.

     5. Settlement. The consummation of the purchase and sale of the FLLP
Membership Interests and the Argo Membership Interests ("Settlement") shall take
place on the date that is thirty (30) days after the expiration of the
Feasibility Study Period (the "Settlement Date"), time being of the essence;
provided, however, that Purchaser shall have the right to postpone the
Settlement Date for thirty (30) days in order to obtain the consent of UBS to
the transactions contemplated by this Agreement, including the Lease
Transactions. Settlement shall occur at such place in the Washington, DC
metropolitan area as is acceptable to Purchaser and Seller.

     6. Pre-Settlement and Settlement Obligations.

          A. Immediately prior to Settlement, Seller (or the applicable Seller,
as set forth below) shall:

               (i) FLLP shall form a single member limited liability company
under the laws of the State of Maryland (the "LLC");

               (ii) FLLP shall transfer FLLP's ownership interest in the
Property (subject to the TIC Agreement) to the LLC by deed in a form reasonably
acceptable to Purchaser;

               (iii) The Argo Sellers shall form a limited liability company
under the laws of the State of Maryland (the "Argo MI Holder" and, together with
the LLC, the "Pass-Through Entities"); and

                                       5

<PAGE>

               (iv) The Argo Sellers shall execute and deliver an assignment of
the Argo Membership Interests to Argo MI Holder and cause Argo MI Holder to
execute an assumption of the Argo Membership Interests, both in forms reasonably
acceptable to Purchaser.

          B. At Settlement, Seller shall:

               (i) Cause FLLP to execute and deliver an assignment of one
hundred percent (100%) of the membership interests in the LLC (the "FLLP
Membership Interests") to Purchaser's designee in a form reasonably acceptable
to Purchaser;

               (ii) Cause Argo MI Holder to execute and deliver an assignment of
the Argo Membership Interests to Purchaser in a form reasonably acceptable to
Purchaser;

               (iii) Deliver to Purchaser copies (and originals where in the
possession or control of Seller) of all available books, records, plans,
studies, data, reports and other materials in Seller's possession or control
relating to or in connection with the Property;

               (iv) Deliver to Purchaser the originals of the Leases (to the
extent in Seller's possession or control) and other agreements executed with
each tenant and all other letters, memoranda and all other records related to
the Leases or tenants;

               (v) Deliver all security deposits and other escrows in Seller's
possession, if any, of tenants occupying space in the Property pursuant to the
Leases as of the date of Settlement;

               (vi) Give full and complete possession of the Property to
Purchaser, not subject to the right of possession by any person or entity other
than the tenants pursuant to the Leases and otherwise pursuant to the Permitted
Exceptions;

               (vii) Deliver to Purchaser copies (and originals where in the
possession of Seller) of all warranties, guarantees, licenses, permits, and
certificates of occupancy which exist for or in respect to the Property;

               (viii) Deliver to Purchaser an affidavit in a form acceptable to
Purchaser and as prescribed in the Foreign Investment in Real Property Transfer
Act of the Internal Revenue Code and the regulations promulgated thereon
("FIRPTA") which certifies that each Seller is not a "foreign person" as defined
therein;

               (ix) Confirm in writing that the representations and warranties
of Seller made in Section 20 remain true and correct as of the Settlement Date;

               (x) Deliver to Purchaser all keys to the Property in Seller's
possession;

               (xi) Provide to Purchaser in Excel format by quarter, the detail
general ledgers and trial balances for the Property for the fiscal year prior to
the closing date and for the interim period from the most recent fiscal year
through the Settlement Date; and

                                       6

<PAGE>

               (xii) Execute and deliver any and all other documents reasonably
required of Seller to consummate the transaction contemplated hereby.

          C. At Settlement, Purchaser shall:

               (i) Deliver or cause to be delivered to Seller the Purchase
Price, as adjusted pursuant to Section 7 hereof;

               (ii) Execute and deliver an assumption of the FLLP Membership
Interests from FLLP in a form reasonably acceptable to Seller;

               (iii) Execute and deliver an assumption of the Argo Membership
Interests in a form reasonably acceptable to Seller; and

               (iv) Execute any and all other documents reasonably required of
Purchaser to consummate the transaction contemplated hereby.

     7. Adjustments. For purposes of calculating prorations, Purchaser shall be
deemed to be in title to the Property, and therefore entitled to the income
therefrom and responsible for the expenses thereof, for the entire day upon
which Settlement occurs. All such prorations shall be made on the basis of the
actual number of days of the year and month that shall have elapsed as of the
Settlement Date. The amount of such prorations shall be adjusted in cash after
Settlement, as and when complete and accurate information becomes available.
Seller and Purchaser agree to cooperate and use their good faith and diligent
efforts to make such adjustments within a reasonable time after the calendar
year end following Settlement. Except as specifically provided otherwise herein,
items of income and expense for the period prior to the Settlement Date will be
for the account of Seller and items of income and expense for the period on and
after the Settlement Date will be for the account of Purchaser, all as
determined by the accrual method of accounting. Bills received after Settlement
that relate to expenses incurred, services performed or other amounts allocable
to the period prior to the Settlement Date shall be paid by Purchaser if such
bills are for Operating Expense Pass-Throughs (as hereinafter defined). The
obligations of the parties pursuant to this Section 7 shall survive Settlement
and shall not merge into any documents of conveyance delivered at Settlement.

          A. REAL ESTATE TAXES AND SPECIAL ASSESSMENTS. Real estate taxes and
assessments imposed by governmental authority (and any assessments imposed by
private covenant) due and payable in the year of Settlement shall be prorated as
of the Settlement Date based upon the most recent tax bills or assessment.
Seller shall receive a credit for any taxes and assessments paid by Owner and
applicable to any period after Settlement. Special assessments shall be prorated
according to the due dates of installments, with Seller being responsible for
installments that become due and payable before the Settlement Date, and
Purchaser being responsible for installments that become due and payable on or
after the Settlement Date. If, for the fiscal tax year in which Settlement is
held, or any prior year, there are any tax protests filed, or abatement
application proceedings pending at any time prior to Settlement with reference
to the Property, Seller shall have the right to settle such protests or
proceedings as long as such settlement does not include any agreement as to the
valuation of the Property for real estate tax purposes for the period after
Settlement. Otherwise, Seller shall not settle the same without

                                       7

<PAGE>

Purchaser's prior written consent. All amounts recovered as a result thereof,
whether by settlement or otherwise, shall, net of attorneys' fees and other
expenses, be apportioned as of Settlement for the fiscal tax year in which
Settlement is held, and paid, when received, to the parties entitled thereto;
provided, however, that to the extent any such amounts are payable to Tenant
pursuant to the terms of the Leases, such amounts shall be promptly paid over to
such Tenant. The parties agree to execute any papers or take such steps, either
before or after any Settlement, as may be necessary to carry out the intention
of the foregoing.

          B. TITLE INSURANCE. Purchaser shall pay all title examination fees of
Title Insurer, the premium for the cost of the Title Insurance Policy with
endorsements and all costs of any lender's title insurance policy, if
applicable.

          C. SURVEY COSTS. Purchaser shall pay all costs of the survey.

          D. SETTLEMENT FEE. Seller and Purchaser will each pay one-half of any
reasonable and customary closing fee charged by the Title Insurer.

          E. TRANSFER TAX. Neither party shall have any obligation for the
payment of any transfer or recordation taxes.

          F. COLLECTED RENTS. All collected net rent (excluding Operating
Expense Pass-Throughs) and other collected income under the Leases shall be
prorated as of Settlement. Seller shall be charged with any rent and other
income collected before Settlement but applicable to any period of time after
Settlement. Uncollected rent and other income shall not be prorated. Purchaser
shall apply rent and other income from Tenants that are collected by Purchaser
after Settlement in the following order: (i) first, to Purchaser's reasonable
third party costs of collection incurred with respect to such Tenant, (ii)
second, to Purchaser in payment of the current rent due under such Lease, (iii)
third, to Purchaser in payment of delinquent rent due under such Leases for the
period from and after Settlement, and (iv) fourth, to Seller in payment of rent
coming due and payable prior to Settlement. Any prepaid rents for the period on
or following the Settlement Date shall be paid over by Seller to Purchaser.
Purchaser will make commercially reasonable efforts, without suit, to collect
any rents relating to the period before Settlement. Seller shall not have the
right to sue delinquent Tenants for delinquent rent after Settlement.

          G. OPERATING EXPENSE PASS-THROUGHS. Owner, as landlord under the
Leases, is currently collecting from Tenants under the Leases additional rent
over an expense stop to cover taxes, insurance, utilities, common area
maintenance and other operating costs and expenses (collectively, "Operating
Expense Pass-Throughs") in connection with the ownership, operation, maintenance
and management of the Property. Seller and Purchaser shall each receive a debit
or credit, as the case may be, for the difference between the Tenants' collected
account balance for Operating Expense Pass-Throughs and the amount of Operating
Expense Pass-Throughs due to or from Tenants as of the Settlement Date.
Operating Expense Pass-Throughs for Seller's period of ownership shall be
reasonably estimated by the parties if final bills are not available. If Owner
was overpaid by any Tenant for the period with respect to any such charges prior
to Settlement, Seller shall remit to Purchaser such estimated overpayment at
Settlement. If Owner was underpaid by any Tenant for the period with respect to
any such charges prior to

                                       8

<PAGE>

Settlement, Seller shall receive a credit at Settlement for the amount of such
estimated underpayment. Any item in this Section 7(g) that is paid directly by
any Tenant pursuant to its Leases shall not be prorated between the parties, and
Purchaser shall look to said Tenant to pay such items. Seller and Purchaser
agree to cooperate and use their good faith and diligent efforts to do a true-up
and make any necessary adjustments to the proration of the Operating Expense
Pass-Throughs within ninety (90) days after the calendar year end following
Settlement.

          H. SECURITY DEPOSITS. Purchaser shall receive a credit against the
Purchase Price in an amount equal to the sum of all unapplied cash security
deposits paid by any Tenant plus, if accrued interest on such security deposits
must be reimbursed to any Tenant that paid a security deposit, all interest
accrued on such security deposits.

          I. INSURANCE. Purchaser hereby acknowledges and agrees that all
insurance maintained on behalf of or with respect to the Owner and the Property
will be terminated as of the Settlement Date.

          J. BANK ACCOUNTS. Seller shall, or shall cause Owner to, close all
bank accounts, lock boxes, other depositories and safe deposit boxes relating to
the Property and all property contained therein, to the extent it relates to the
Property shall be delivered or transferred to the bank accounts, lock boxes,
other depositories and safe deposit boxes designated by Purchaser. Purchaser
shall, or shall cause Owner to, establish new bank accounts, lock boxes, other
depositories and safe deposit boxes, to the extent it deems necessary to operate
the business of the Owner and the Property from and after the Settlement Date.

          K. OTHER COSTS. All other costs shall be allocated in accordance with
the customs prevailing in similar transactions in the Washington, DC
metropolitan area.

     8. Feasibility Study Period.

          A. Seller shall, to the extent it has not previously done so, within
two (2) business days after mutual execution of this Agreement, deliver to
Purchaser the documents listed on EXHIBIT E, to the extent the same are in
Seller's or Owner's possession or control. Purchaser shall have until 5:00 p.m.
Eastern Time on April 21, 2006 (the "Feasibility Study Period"), to complete
certain inspections of the Property (including, without limitation, any
environmental and engineering inspections of the Property). During the
Feasibility Study Period, Purchaser, its agents and representatives shall be
entitled to make such investigations, studies and inspections of the Property as
it deems necessary in order for it to make a determination as to whether the
Property is suitable for its intended purpose, provided that (i) Purchaser shall
only undertake intrusive testing of the Property following notice to and receipt
of written consent from Seller, and (ii) Purchaser shall not contact or disturb
any tenants at or about the Property without Seller's prior written consent and
all such contact with any tenant shall be coordinated through Seller and Seller
shall have the opportunity to be present thereat. In the event Purchaser, in its
sole and absolute discretion, provides Seller with written notice, prior to 5:00
p.m. Eastern Time on the final day of the Feasibility Study Period, of
Purchaser's intention not to proceed to Settlement hereunder, the Title Insurer
shall immediately return the Deposit to Purchaser, this Agreement shall
terminate as of such date, and neither party shall have any further right or
obligation hereunder other than those which by their express terms survive such
termination. In

                                       9

<PAGE>

the event Purchaser fails to provide notice of termination as aforesaid,
Purchaser shall be deemed to have accepted the Property and the status of title
thereto as of such date, this Agreement shall remain in full force and effect in
accordance with its terms.

          B. Purchaser, its agents and representatives shall have the right
during normal business hours and in coordination with Seller's management agent,
to enter upon the Property prior to Settlement for the purpose of making any
inspection, investigations, studies or tests. Purchaser shall repair any damage
to the Property resulting from any inspections, studies or tests performed by
Purchaser. In connection with such entry onto the Property, Purchaser agrees
that it shall be responsible for any damages to the same resulting from such
operations and shall indemnify and hold Seller harmless from all claims of any
type arising out of or incident to Purchaser's entry onto the Property.
Purchaser's obligations under this Section 8.B. shall survive Settlement or any
other termination of this Agreement. Prior to any entry on the Property,
Purchaser shall deliver to Seller a policy of comprehensive general liability
insurance, with a combined single limit of not less than $2,000,000 per
occurrence, naming Seller and its management agent as additional insureds, and
insuring against loss or damage resulting from Purchaser's entry on the
Property.

          C. Seller agrees that, subsequent to the expiration of the Feasibility
Study Period, provided Purchaser has not terminated this Agreement as set forth
in Section 8.A. above, Seller shall not execute any leases, licenses or other
rental or occupancy agreements for vacant space within the Improvements, without
the prior consent of Purchaser.

          D. The parties acknowledge that Purchaser may be required to perform a
historical audit of the Property in order to comply with Item 3-14 of Regulation
S-X promulgated under the Securities Act of 1933 and the Securities Exchange Act
of 1934. Seller shall, effective with the Settlement Date, make commercially
reasonable efforts to permit Purchaser's auditors access at that location where
Owner customarily maintains its records, upon reasonable advance notice and
during normal business hours, to all of the Property's books and records and the
operating statements (certified by an officer of Seller or of the general
partner of Seller) and property management balance sheets for the Property for
one (1) calendar year prior to the Settlement Date and for the period from the
end of the prior fiscal year through the Settlement Date. To the extent that the
originals or copies of same are not otherwise provided by Seller to Purchaser at
Settlement, and to the extent that the same are ordinarily maintained by Seller
in its normal course of business, such books and records shall include the
detail general ledger of profits and loss, accounts receivable records, rent
rolls, billing records, accounts payable records all contracts. Buyer's access
rights shall commence on the Settlement Date and shall continue until the
successful completion of the audit and the filing of the 3-14 report with the
SEC, written notice of which shall be delivered promptly by Purchaser to Seller.
The foregoing obligation shall fully survive Settlement. Notwithstanding
anything to the contrary in the foregoing, other than providing the access to
Purchaser specified herein, Seller shall not have any liability or
responsibility in connection with or in any manner related to, directly or
indirectly, any audit required to be made by Purchaser or any compliance
required of Purchaser with any Regulation under the Securities Act of 1933 or
the Securities Act of 1934.

     9. Condemnation. In the event Seller or Owner receives notice of any
material condemnation proceedings or notice of the intention of any governmental
or quasi-governmental

                                       10

<PAGE>

authority to initiate condemnation proceedings involving a material portion of
the Property, or if any such proceedings commence, or an actual condemnation or
taking of a material portion of the Property or any portion thereof occurs,
Seller will promptly notify Purchaser and Purchaser may, within fifteen (15)
days thereafter (i) elect to terminate this Agreement, in which event, the
Deposit shall be returned to Purchaser, and the parties shall be relieved of all
further liability hereunder, except those obligations herein that expressly
survive the termination of this Agreement; or (ii) if Purchaser does not elect
to terminate this Agreement the condemnation award as well as any unpaid claims
or rights in connection with such condemnation shall be assigned to Purchaser at
Settlement, or, if paid to Seller prior to Settlement, shall be credited at
Settlement against and up to the amount of the Purchase Price. Provided that the
Feasibility Study Period has expired and Purchaser has given written notice of
its intention to proceed with Settlement hereunder notwithstanding any such
proceeding, Purchaser shall have the right to participate with Seller (all
action after such time until Settlement to be upon mutual agreement of the
parties) in the negotiations and settlement of any condemnation claim.

     10. Casualty Loss. In the event that subsequent to the date hereof any part
of the Property is damaged or destroyed by fire or other casualty and the cost
of repair thereof is in excess of Five Hundred Thousand Dollars ($500,000.00) (a
"Material Casualty"), Seller will promptly notify Purchaser, and Purchaser may,
at its option, by giving written notice to Seller within ten (10) business days
after receipt from Seller of notice of Seller's estimate of restoration of the
Property caused by such casualty, terminate this Agreement. In such event
Purchaser shall be entitled to the return of the Deposit, and thereafter neither
Purchaser nor Seller shall have any further liability to the other hereunder,
except for any obligations herein that expressly survive the termination of this
Agreement. In the event of a casualty which is not a Material Casualty, or in
the event of a Material Casualty as a result of which Purchaser does not elect
to terminate this Agreement, and provided that the Feasibility Study Period has
expired and Purchaser has given written notice of its intention to proceed with
Settlement hereunder, Purchaser shall be obligated to proceed to Settlement in
accordance with this Agreement and all insurance proceeds in connection with
such casualty, plus the amount of Owner's deductible, less such amount as
previously expended by Owner in the repair of such casualty, shall be assigned
to Purchaser at Settlement or, if paid to Owner prior thereto, shall be credited
against the unpaid Purchase Price due at Settlement.

     11. Default.

          A. If Purchaser without cause shall fail or refuse to make Settlement
hereunder, the amount of damages not being ascertainable, the Deposit shall be
forfeited and the same shall forthwith be delivered by the Title Insurer to
Seller as liquidated damages. In the event of such default by Purchaser,
Seller's sole remedy shall be restricted to retention of said Deposit, and
Purchaser shall have no other responsibility or liability of any kind to Seller
by virtue of such default.

          B. If Seller, through no fault of Purchaser, shall fail to perform its
obligations hereunder to make full Settlement in accordance with the terms
hereof, the sole and exclusive remedy of Purchaser shall be either the right to
terminate this Agreement and have the Deposit promptly returned to Purchaser, or
the right to specific performance to enforce Seller's obligation to consummate
Settlement hereunder.

                                       11

<PAGE>

          C. The representations of Seller contained in this Agreement shall
survive Settlement; provided, however, (i) any cause of action of Purchaser
against Seller by reason of a breach or default of any of the representations
set forth herein or in any certificates executed by Seller pursuant to this
Agreement shall automatically expire as of the date which is twelve (12) months
after Settlement (the "Warranty Expiration Date"), except that the same shall
not expire as to any such breach or default as to which Purchaser has given
written notice to Seller of a claim for any such breach or default prior to the
Warranty Expiration Date, (ii) no action shall be brought against Seller as a
result of any alleged breach of a representation or warranty unless and until
the amount at issue as a result thereof (including all such alleged breached in
the aggregate) is in excess of $50,000.00, and (iii) Seller's total liability
for any breach or breaches of its representations set forth herein shall in no
event exceed $1,000,000.00 in the aggregate, which liability limit shall survive
Settlement. The Warranty Expiration Date and the foregoing limitations on
Seller's liability shall be inapplicable to any breach of a Seller's warranty
under or pursuant to Section 13.U. hereof.

          D. In the event of litigation by either party to enforce its rights
hereunder, the prevailing party in any such action shall be entitled to recover
from the other its court costs and reasonable and actual attorneys' fees
incurred in the pursuit of such action.

     12. Broker. Each party, by the execution hereof, represents and warrants
that neither party has engaged the services of any broker, finder, agent or
other person or entity in connection with this transaction other than Advantis
Real Estate Services Company which shall be paid a fee by Seller upon (and only
in the event of) consummation of Settlement hereunder, pursuant to separate
agreement. Each party shall indemnify and hold harmless the other against and
from any loss, cost, damage or fee resulting from any inaccuracy of such
representation and warranty.

     13. Seller's Representations and Warranties. Seller hereby represents and
warrants the following to Purchaser, all of which representations and warranties
shall be true and complete as of Settlement:

          A. AUTHORITY. Each Seller and Pass-Through Entity which is an entity
(as opposed to a natural person) is duly qualified and validly existing in good
standing under the laws of the state of its organization and is (or, in the case
of the Pass-Through Entities, on the Settlement Date, will be) qualified to do
business in the State of Maryland. The execution and delivery of this Agreement
has been, and the performance of each such Seller's and Pass-Through Entity's
obligations hereunder will be, duly authorized by all necessary action on the
part of each Seller and Pass-Through Entity, and this Agreement constitutes the
legal, valid, binding and enforceable obligation of each Seller, subject to
equitable principles and principles governing creditors' rights generally.
Attached to this Agreement as Exhibit K, Exhibit L and Exhibit M are true,
correct and complete copies of (i) the Limited Partnership Agreement of Foulger,
and (ii) the tenancy in common agreement between Foulger and Argo and (iii) the
Operating Agreement of Argo.

          B. FIRPTA. Neither any person or entity constituting Seller, the
Pass-Through Entities nor Owner is a "foreign person," "foreign partnership,"
"foreign trust" or "foreign estate" as those terms are defined in Section 1445
of the Internal Revenue Code.

                                       12

<PAGE>

          C. PROCEEDINGS. To the knowledge of Seller, there is no action,
litigation, investigation, condemnation or proceeding of any kind pending or, to
the knowledge of Seller, threatened against Seller, the Pass-Through Entities or
Owner which would have a material and adverse affect on the ability of Seller to
perform its obligations under this Agreement, or related to the Subject Property
or the Leases other than as disclosed to Purchaser in writing.

          D. LEASES.

               (i) EXHIBIT D is a true and complete list of the Leases and all
other occupancy agreements relating to the Property. Except as set forth in the
Leases, there are no rights of first refusal, options to terminate without cause
of Owner, options to renew, options to purchase, or any rent abatements given to
tenant under the Leases (the "Tenant") after the Tenant is in occupancy and
paying rent.

               (ii) To the Seller's knowledge, each Lease is in full force and
effect according to the terms set forth therein, and there is no modification,
amendment or alteration in writing or otherwise, except as set forth in EXHIBIT
D.

               (iii) To Seller's knowledge there are not, and neither Seller nor
Owner has received written notice from any Tenant of any unperformed obligation
of the Owner, as landlord under any of the Leases, including, without
limitation, failure of the landlord to construct any required tenant
improvements. Neither Seller nor Owner has been advised in writing of any claims
or disputes giving rise to any setoff by Tenant. With respect to the Leases, all
tenant improvement allowances have been paid and all tenant improvements have
been completed. As of the Settlement Date, no Tenant shall be entitled to any
free rent under any Lease.

               (iv) Neither Owner nor any Tenant is in default under the Leases
(beyond any applicable grace or cure period), and there are no rent
delinquencies of more than thirty (30) days.

               (v) There are no brokers' commissions, finders' fees, or other
charges payable or to become payable to any third party on behalf of Seller or
Owner as a result of or in connection with the Leases, including, without
limitation, any unexecuted options to expand or renew, except as set forth on
the rent roll attached as EXHIBIT F (the "Rent Roll").

               (vi) Except as set forth on the Rent Roll, (i) no rent has been
paid by any Tenant more than one month in advance and (ii) no unapplied security
deposits have been paid by any Tenant.

     The foregoing terms and provisions of this subsection 13.D shall be deemed
replaced, and Seller's representations concerning the Leases shall be
terminated, as of such time as an Estoppel Certificate (as herein defined) is
received under and pursuant to each such Lease.

          E. BLOCKED PERSONS. Seller has not received written notice that either
any party constituting Seller, the Pass-Through Entities or Owner is:

                                       13

<PAGE>

               (i) listed on the Specially Designated Nationals and Blocked
Persons List maintained by the Office of Foreign Assets Control, Department of
the Treasury ("OFAC") pursuant to Executive Order No. 13224, 66 Fed. Reg. 49079
Sept. 25, 2001 (the "Order") and/or on any other list of terrorists or terrorist
organizations maintained pursuant to any of the rules and regulations of OFAC or
pursuant to any other applicable Orders (such lists are collectively referred to
as the "Lists");

               (ii) a person who has been determined by competent authority to
be subject to the prohibitions contained in the Order;

               (iii) owned or controlled by, and does not act for or on behalf
of, any person or entity on the Lists or any other person or entity who has been
determined by competent authority to be subject to the prohibitions contained in
the Order.

          F. BANKRUPTCY. Neither any party constituting Seller, the Pass-Through
Entities nor Owner is the subject of, and neither has received any written
notice of or threat that either of them has or will become the subject of, any
reorganization, liquidation, dissolution, receivership or other action or
proceeding under the United States Bankruptcy Code, 11 U.S.C. Sections 101, et
seq., or any other federal, state or local laws affecting the rights of debtors
and/or creditors generally, whether voluntary or involuntary and including,
without limitation, proceedings to set aside or avoid any transfer of any
interest in property or obligations, whether denominated as a fraudulent
conveyance, preferential transfer or otherwise, or to recover the value thereof
or to charge, encumber of impose a lien thereon.

          G. CONTRACTS. EXHIBIT C attached hereto is a complete list of all
current Contracts which list includes the names of the contracting parties, the
dates of the Contracts and a listing of all amendments to such Contracts.

          H. CONDEMNATION. To the best of Seller's knowledge, Seller has no
knowledge of nor has it or Owner received any written notice of any pending or
contemplated condemnation proceedings affecting all or any part of the Property.

          I. ACCURACY OF DOCUMENTS. All documents and records to be delivered
comprising the Property Information are true, correct and complete copies of the
documents and records purported to be delivered thereunder as appear in Seller's
(or Owner's) files as of the date hereof (provided the foregoing is not intended
and shall not be construed to constitute a representation or warranty as to the
accuracy or completeness of the content of any such document prepared by any
third party).

          J. TITLE TO MEMBERSHIP INTERESTS. As of the date hereof, the Argo
Sellers are the record and beneficial owner of all of the Argo Membership
Interests. As of the Settlement Date, Argo MI Holder will be the record and
beneficial owner of all of the Argo Membership Interests and FLLP will be the
record and beneficial owner of all of the FLLP Membership Interests. As of the
Settlement Date, the Argo Membership Interests will constitute 100% of all of
the outstanding membership interests of Argo free and clear of all right, claim
and interest of others. As of the Settlement Date, the FLLP Membership Interests
will constitute

                                       14

<PAGE>

100% of all outstanding partnership interests of the LLC free and clear of all
right, claim and interest of others

          K. LOAN ESCROW ACCOUNTS. Attached hereto as EXHIBIT N is a true and
accurate list of all escrow accounts (and the amount of each such escrow
account) held by UBS in connection with the Loan.

          L. SUBSIDIARIES. Except for the LLC, neither Owner nor the LLC has any
subsidiaries nor any investments or other interests in (including advances to)
any other business, person or venture.

          M. FINANCIAL STATEMENTS. Seller has furnished Purchaser with copies of
the balance sheet of Owner as of January 31, 2006 and the related statement of
earnings for the period ending on such date (hereinafter collectively referred
to as the "Financial Statements"). To the best of Seller's knowledge, the
Financial Statements (a) are in accordance with the books and records of Owner,
(b) present fairly (i) the assets, liabilities and financial condition of Owner
as of such date, and (ii) the results of operations for the period covered
thereby, and (c) have been prepared on a tax basis consistent with that of
preceding years. Since the date of the Financial Statements, there has not been
any material adverse change in the financial condition, business, properties or
results of operations of Owner.

          N. ACTIONS BY OWNER AND LLC SINCE THE DATE OF THE FINANCIAL
STATEMENTS. Since the date of the Financial Statements, unless otherwise
disclosed, neither Owner nor the LLC has:

               (i) incurred or agreed to incur any obligations or liabilities,
except obligations or liabilities in the ordinary course of business, or under
contracts, leases, documents and transactions listed in the attached exhibits or
incurred or agreed to incur any debt;

               (ii) satisfied or discharged any lien, or paid any obligation or
liabilities other than (A) liabilities included in the Financial Statements, (B)
liabilities incurred in the ordinary course of business, and (C) obligations and
liabilities under contracts, leases, transactions or documents listed in the
attached exhibits;

               (iii) mortgaged, pledged or subjected to lien or other
encumbrance any of its property;

               (iv) sold or transferred any of its assets or canceled any debts
owing to it or claims owed by it;

               (v) waived any rights of material value;

               (vi) experienced any material change in the financial condition,
or in the operations or business of Owner, other than changes in the ordinary
course of business; or

               (vii) suffered any damage or destruction, whether or not covered
by insurance, materially and adversely affecting the properties or business of
Owner or the LLC.

                                       15

<PAGE>

          O. LIABILITIES. Neither Owner nor the LLC has any debts, liabilities,
or obligations of, or claims of any kind or character, whether accrued, absolute
or contingent ("Liabilities") other than Liabilities reflected on the Financial
Statements and trade payables incurred in the ordinary course of business and to
be adjusted as provided herein.

          P. COMPLIANCE WITH LEGAL REQUIREMENTS. To the knowledge of Seller,
Owner is in material compliance with all applicable laws, ordinances, rules,
regulations, orders and requirements of all governmental authorities relating
to, or regulating, the activities of Owner.

          Q. CERTAIN PROPERTY OBLIGATIONS. As of the date hereof: (a) all
payments, levies, dues, charges, assessments and other amounts (except for real
estate taxes, special assessments and front foot benefit or private utility
charges not yet due and payable) which are payable on or before the date hereof
affecting the Property ("Title Documents") which, to Seller's knowledge, exist,
are paid in full (except for financings of record and insurance premiums), and
(b) to Seller's Knowledge, there are no existing defaults or violations
affecting the Property or the obligations of the Owner under the Title
Documents.

          R. ALL CONTRACTS. Seller has furnished to Purchaser copies of all
Contracts as are kept in Owner's files in the ordinary course of business.

          S. LITIGATION. There is no action, suit, litigation, judicial
proceeding or governmental investigation (collectively, the "Actions") pending,
or to Seller's Knowledge, threatened, against or relating to the business of
Owner or involving any of its property which, if adversely determined, could
reasonably be expected to have a material adverse effect on Owner or the
Property. Owner does not currently have pending, and is not considering, any
litigation or the pursuit of any rights or remedies that may be available
against any third parties relating to the business of the Owner or involving any
of its property.

          T. TAX MATTERS.

               (i) Owner, the LLC and Seller have filed all Tax Returns required
to be filed by either of them involving Owner or the LLC prior to the date
hereof. To Owner's and Seller's respective knowledge, all such filed Tax Returns
were correct and complete in all material respects and all Taxes owed by or on
behalf of Owner or the LLC (whether or not shown on any Tax Return) have been
paid. To Owner's and Seller's respective knowledge, Owner has complied in all
material respects with all applicable laws, rules and regulations relating to
the payment and withholding of Taxes and Owner or the LLC or Seller, as
appropriate, has withheld and paid over to the proper governmental entities,
within the time period prescribed by law, all material amounts required to be so
withheld and paid over under applicable laws and regulations. Neither Owner nor
the LLC is the beneficiary of any extension of time within which to file a Tax
Return involving Owner or the LLC, except for an extension to July 15, 2006
(which Tax Return shall be filed and all taxes thereunder paid prior to
Settlement). Since the date of such Financial Statements, Owner has not incurred
any material liability for Taxes other than in the ordinary course of business.
To Seller's Knowledge, no event has occurred, and no condition or circumstance
exists, which presents a material risk that any material Tax described in the
preceding sentences will be imposed upon Owner or the LLC.

                                       16

<PAGE>

               (ii) Neither Owner nor the LLC is the subject of any audit,
examination, or other proceeding in respect of Taxes, and Seller has no actual
knowledge that any audit, examination or other proceeding in respect of Taxes
involving Owner or the LLC is being considered by any Tax authority. No
deficiencies for any Taxes have been proposed, asserted or assessed against
Owner or the LLC. Neither Owner, the LLC nor Seller has given any currently
effective waiver of any statute of limitations in respect of Taxes involving
Owner or the LLC or agreed to any currently effective extension of time with
respect to a Tax assessment or deficiency involving Owner or the LLC. There are
no liens (other than for Taxes not yet due and payable) on any of the assets of
Owner or the LLC that arose in connection with any failure (or alleged failure)
to pay any Tax.

               (iii) There is no dispute or claim concerning any Tax liability
involving Owner or the LLC either (A) claimed or raised by any governmental
authority in writing or (B) to the knowledge of Seller, based upon personal
contact with any agent of such authority, which remains unsettled as of the date
hereof.

               (iv) Neither Owner nor the LLC is liable for any Taxes
attributable to any other Person, whether by reason of being a member of an
affiliated group, being a party to a tax sharing agreement, as a transferee or
successor, or otherwise.

               (v) No powers of attorney or other authorizations are in effect
that grant to any Person the authority to represent Owner, the LLC or Seller in
connection with any Tax matter or proceeding involving Owner or the LLC.

               (vi) Owner has delivered to Purchaser correct and complete copies
of any Tax Returns and reports Owner filed for all periods not barred by the
applicable statute of limitations. With respect to periods not barred by the
applicable statute of limitations, Schedule (i) describes all material Tax
elections, consents and agreements made by or affecting Owner or any Person to
whose liabilities Owner has succeeded that will be in effect after the
Settlement Date, (ii) lists all material types of Taxes paid and Tax Returns
filed by or on behalf of Owner or any such Person, (iii) expressly indicates
each Tax with respect to which Owner or any such Person is or has been included
in a consolidated, unitary or combined Tax Return, and (iv) describes the status
of all examinations, administrative or judicial proceedings, and litigation with
respect to any Taxes of Owner or for which it may be liable. The LLC has never
been required to pay taxes or file any tax return.

               (vii) Owner has delivered to Purchaser any depreciation,
amortization, or tax basis information necessary for the preparation of
Purchaser's tax returns.

          U. PRIOR ACTIVITIES OF OWNER AND THE LLC. Neither Owner nor the LLC
has, directly or indirectly, engaged in any business or activity other than
owning the Property and those businesses and activities incidental thereto.

          V. BINDING EFFECT: APPROVALS AND CONSENTS. Subject to approval by UBS
of the transactions contemplated hereby, Seller's execution and delivery of this
Agreement and performance of the transactions contemplated hereby will not
result in a breach or violation by Owner, the Pass-Through Entities or Seller
of, or constitute a default by Owner, the Pass-

                                       17

<PAGE>

Through Entities or Seller under, any agreement or instrument to which Owner,
the Pass-Through Entities or Seller is a party or by which any of its properties
are bound, or the organizational documents of Owner, the Pass-Through Entities
or Seller, or any statute, judgment, order, injunction, decree, regulation or
ruling of any court or other governmental authority.

          W. INSURANCE. Owner currently maintains insurance of the types, in the
amounts and insuring against the risks as set forth in EXHIBIT G. Seller and
Purchaser acknowledge and agree that all policies of insurance currently held by
Owner will be cancelled or Owner will be removed as an insured or beneficiary
thereunder at Settlement.

          X. BANKING RELATIONSHIPS. EXHIBIT H attached hereto lists all bank
accounts of Owner and the persons authorized to make withdrawals therefrom, all
lock boxes and other depositories maintained by or on behalf of Owner and the
persons authorized to make withdrawals therefrom or have access thereto, and all
safe deposit boxes of Owner and the persons authorized to obtain access to such
safe deposit boxes.

          Y. EMPLOYEES. Neither Owner nor the LLC has any employees.

     For purposes of this Section 13, the following capitalized terms shall have
the following meanings:

     "Tax" or "Taxes" shall mean any federal, state, local or foreign income,
gross receipts, license, payroll, employment, excise, severance, stamp,
occupation, premium, windfall profits, environmental (including taxes under Code
Section 59A), customs duties, capital stock, franchise, profits, withholding,
social security (or similar), unemployment, disability, real property, real
estate taxes, personal property, sales, use, transfer, registration, value
added, alternative or add-on minimum, estimated or other tax of any kind
whatsoever involving Owner, including any interest, penalty or addition thereto,
whether disputed or not.

     "Tax Return" means any return, declaration, report, claim for refund, or
information return or statement relating to Taxes, including any schedule or
attachment thereto, and including any amendment thereof.

     All references in this Agreement to "to the best of Seller's knowledge,"
"Seller's actual knowledge" or words of similar import shall refer only to the
actual (as opposed to deemed, imputed or constructive) knowledge of Richard L.
Perlmutter and John Austin, without inquiry, and notwithstanding any fact or
circumstance to the contrary, shall not be construed to refer to the knowledge
of any other person or entity. Such individuals are named in this Agreement
solely for the purpose of establishing the scope of Seller's knowledge. Such
individuals shall not be deemed to be a party to this Agreement nor to have made
any representations or warranties personally, and no recourse shall be had to
such individuals for any of Seller's representations and warranties hereunder,
and Purchaser hereby waives any liability of or recourse against such
individuals.

                                       18

<PAGE>

     Except as is otherwise expressly provided in this Agreement, Seller hereby
specifically disclaims any warranty (oral or written) concerning: (i) the nature
and condition of the Property and the suitability thereof for any and all
activities and uses that Purchaser elects to conduct thereon; (ii) the manner,
construction, condition and state of repair or lack of repair of the
Improvements; (iii) the compliance of the Land and the Improvements or their
operation with any laws, rules, ordinances or regulations of any government or
other body; and (iv) any other matter whatsoever except as expressly set forth
in this Agreement.

     EXCEPT AS IS OTHERWISE EXPRESSLY PROVIDED IN THIS AGREEMENT, THE SALE OF
THE PROPERTY IS MADE ON A STRICTLY "AS IS" "WHERE IS" BASIS AS OF THE SETTLEMENT
DATE, AND SELLER MAKES NO WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED, OR
ARISING BY OPERATION OF LAW, INCLUDING, BUT IN NO WAY LIMITED TO, ANY WARRANTY
OF QUANTITY, QUALITY, CONDITION, HABITABILITY, MERCHANTABILITY, SUITABILITY OR
FITNESS FOR A PARTICULAR PURPOSE OF THE PROPERTY OR THE PROPERTY, ANY
IMPROVEMENTS LOCATED THEREON OR ANY SOIL CONDITIONS RELATED THERETO.

     PURCHASER SPECIFICALLY ACKNOWLEDGES THAT PURCHASER IS NOT RELYING ON (AND
SELLER HEREBY DISCLAIMS AND RENOUNCES) ANY REPRESENTATIONS OR WARRANTIES MADE BY
OR ON BEHALF OF SELLER OF ANY KIND OR NATURE WHATSOEVER, EXCEPT FOR THOSE
PARTICULAR REPRESENTATIONS AND WARRANTIES EXPRESSLY PROVIDED IN THIS AGREEMENT.
FURTHER, PURCHASER, FOR PURCHASER AND PURCHASER'S SUCCESSORS AND ASSIGNS, HEREBY
RELEASES SELLER FROM, AND WAIVES, ANY AND ALL CLAIMS AND LIABILITIES AGAINST
SELLER FOR, RELATED TO, OR IN CONNECTION WITH, ANY ENVIRONMENTAL OR PHYSICAL
CONDITION AT THE PROPERTY (OR THE PRESENCE OF ANY MATTER OR SUBSTANCE RELATING
TO THE ENVIRONMENTAL CONDITION OF THE PROPERTY), INCLUDING, BUT NOT LIMITED TO,
CLAIMS AND/OR LIABILITIES RELATING TO (IN ANY MANNER WHATSOEVER) ANY HAZARDOUS,
TOXIC OR DANGEROUS MATERIALS OR SUBSTANCES LOCATED IN, AT, ABOUT OR UNDER THE
PROPERTY, OR FOR ANY AND ALL CLAIMS OR CAUSES OF ACTION (ACTUAL OR THREATENED)
BASED UPON, IN CONNECTION WITH, OR ARISING OUT OF, CERCLA, AS AMENDED BY SARA,
AND AS MAY BE FURTHER AMENDED FROM TIME TO TIME, RCRA, OR ANY OTHER CLAIM OR
CAUSE OF ACTION (INCLUDING ANY FEDERAL OR STATE BASED STATUTORY, REGULATORY OR
COMMON LAW CAUSE OF ACTION) RELATED TO ENVIRONMENTAL MATTERS OR LIABILITY WITH
RESPECT TO, OR AFFECTING, THE PROPERTY. PURCHASER REPRESENTS TO SELLER THAT
PURCHASER HAS CONDUCTED, OR WILL CONDUCT PRIOR TO SETTLEMENT, SUCH
INVESTIGATIONS OF THE PROPERTY, INCLUDING BUT NOT LIMITED TO, THE PHYSICAL AND
ENVIRONMENTAL CONDITIONS THEREOF, AS PURCHASER DEEMS NECESSARY TO SATISFY ITSELF
AS TO THE CONDITION OF THE PROPERTY AND THE EXISTENCE OR NONEXISTENCE OF, OR
CURATIVE ACTION TO BE TAKEN WITH RESPECT TO, ANY HAZARDOUS OR TOXIC SUBSTANCES
ON OR DISCHARGED FROM THE LAND OR THE IMPROVEMENTS, AND WILL RELY SOLELY UPON
SAME AND NOT UPON ANY INFORMATION PROVIDED BY, OR ON

                                       19

<PAGE>

BEHALF OF, SELLER, ITS AGENTS AND EMPLOYEES WITH RESPECT THERETO, OTHER THAN
SUCH REPRESENTATIONS AND WARRANTIES OF SELLER AS ARE EXPRESSLY SET FORTH IN THIS
AGREEMENT. UPON SETTLEMENT, PURCHASER SHALL ASSUME THE RISK THAT ADVERSE
MATTERS, INCLUDING BUT NOT LIMITED TO, CONSTRUCTION DEFECTS AND ADVERSE PHYSICAL
AND ENVIRONMENTAL CONDITIONS, MAY NOT HAVE BEEN REVEALED BY PURCHASER'S
INVESTIGATIONS, AND PURCHASER, UPON SETTLEMENT, SHALL BE DEEMED TO HAVE WAIVED,
RELINQUISHED AND RELEASED SELLER FROM AND AGAINST ANY AND ALL CLAIMS, DEMANDS,
CAUSES OF ACTION (INCLUDING CAUSES OF ACTION IN TORT), LOSSES, DAMAGES,
LIABILITIES, COSTS AND EXPENSES (INCLUDING ATTORNEYS' FEES AND COURT COSTS) OF
ANY AND EVERY KIND OR CHARACTER, KNOWN OR UNKNOWN, WHICH PURCHASER MIGHT HAVE
ASSERTED OR ALLEGED AGAINST SELLER, AT ANY TIME BY REASON OF OR ARISING OUT OF
ANY LATENT OR PATENT CONSTRUCTION DEFECTS OR PHYSICAL CONDITIONS, VIOLATIONS OF
ANY APPLICABLE LAWS (INCLUDING, WITHOUT LIMITATION, ANY ENVIRONMENTAL LAWS) AND
ANY AND ALL OTHER ACTS, OMISSIONS, EVENTS, CIRCUMSTANCES OR MATTERS REGARDING
THE PROPERTY.

     PURCHASER ACKNOWLEDGES AND AGREES THAT THE WAIVERS, RELEASES AND OTHER
PROVISIONS CONTAINED IN THIS SECTION 13 WERE A MATERIAL FACTOR IN SELLER'S
ACCEPTANCE OF THE PURCHASE PRICE AND THAT SELLER IS UNWILLING TO SELL THE
PROPERTY (AND THE PROPERTY) TO PURCHASER UNLESS SELLER IS RELEASED AS EXPRESSLY
SET FORTH ABOVE. PURCHASER, WITH PURCHASER'S COUNSEL, HAS FULLY REVIEWED THE
DISCLAIMERS AND WAIVERS SET FORTH IN THIS AGREEMENT, AND UNDERSTANDS THE
SIGNIFICANCE AND EFFECT THEREOF. THE TERMS AND CONDITIONS OF THIS SECTION 13 (C)
WILL EXPRESSLY SURVIVE SETTLEMENT, WILL NOT MERGE WITH THE PROVISIONS OF ANY
SETTLEMENT DOCUMENTS, AND WILL BE INCORPORATED INTO THE DEED.

     Any claim by Purchaser based upon an alleged breach of any representation
or warranty of or by Seller contained herein is intended and shall specifically
be limited by the provisions of Section 11.C. hereof.

     14. Covenants by Seller. Seller covenants and agrees with Purchaser that
from the date hereof until the Settlement Date (as herein defined), Seller shall
cause Owner to conduct its business involving the Property as follows, and
during such period will (except as specifically provided to the contrary
herein):

          A. Refrain from creating on the Property any easements, encumbrances
or liens affecting the Property other than as may be required by any applicable
governmental or quasi-governmental authority or by a provider of utility
services, and refrain from removing any Personal Property, fixture or equipment;
provided, however, nothing herein shall preclude Seller or Owner from replacing
any such items in the ordinary course of operating the Property. Seller shall,
upon Seller's receipt, deliver to Purchaser a copy of any easement so required
by any governmental or quasi-governmental authority or provider of utility
services affecting the

                                       20

<PAGE>

Property which does not require the consent of Purchaser, and any such easement
shall constitute a Permitted Encumbrance.

          B. Refrain from entering into or amending the Contracts (other than
Leases which are governed by Section 14D below) regarding the Property (other
than contracts in the ordinary course of business which are cancelable by Owner
without penalty within thirty (30) days after giving notice thereof) without the
prior written consent of Purchaser, which consent shall not be unreasonably
withheld, delayed or conditioned, and which shall be deemed given if Purchaser
does not object to Seller's request for approval within five (5) business days.

          C. Operate, maintain, repair and insure the Property in a commercially
reasonable manner consistent with the existing operation, maintenance, repair
and insurance of the Property and deliver the Property as of Settlement
substantially in the condition it is in of the date hereof, ordinary wear and
tear, and damage by fire or other casualty excepted (provided that neither
Seller nor Owner shall be obligated to incur costs in excess of $50,000.00 in
connection with such operation, maintenance and/or repair).

          D. Except as expressly provided herein, from and after the date hereof
(provided that this Agreement has not been terminated), Owner shall refrain from
amending the existing Leases without Purchaser's written approval, as provided
below. In addition, from and after the date hereof (provided that this Agreement
has not been terminated), except as expressly provided herein, Seller shall not
permit Owner to enter into any new leases with respect to the Property (each a
"Proposed New Lease"), without Purchaser's written approval, as provided in this
Section 14D. Seller shall furnish Purchaser with a true and correct copy of any
Proposed New Lease into which Owner desires to enter and such financial
information with respect to the proposed tenant as Seller has in its possession.
Purchaser shall have three (3) business days from receipt of such amendment or
Proposed New Lease to approve or disapprove the same, which approval shall not
be unreasonably withheld, conditioned or delayed. In the event that Purchaser
does not approve any such amendment or Proposed New Lease, Purchaser shall
notify Seller, in writing, of such disapproval prior to expiration of the
aforesaid three (3) business day period, stating in such written notification
under what conditions, if any, Purchaser's approval would be forthcoming and
Purchaser's agreement to approve such amendment or Proposed New Lease if such
conditions are satisfied. Notwithstanding the foregoing, Purchaser and Seller
acknowledge and agree that Owner may enter into a new Lease (the "Nextone
Lease") with Nextone Corporation ("Nextone") and a new Lease (the "Harvey Cleary
Lease") with Harvey Cleary, both upon the terms and conditions set forth on
EXHIBIT I. The Nextone Lease shall also provide that Nextone has waived its
right to terminate its 1st floor lease for 11,392 sf and waived its right to
apply the tenant improvement allowance towards rent abatement. All other terms
of the Nextone Lease and the Harvey Cleary Lease shall be subject to Purchaser's
approval as set forth above. Notwithstanding the foregoing, if Seller does not
complete the Lease Transactions, it shall not be a breach of this Paragraph or a
default by Seller or Owner hereunder. The foregoing is not intended and shall
not be construed to prohibit Owner or Seller from entering into any amendment to
a Lease pursuant to a validly exercised renewal or expansion right on the part
of any Tenant as is specifically set forth in its Lease.

          E. Promptly provide Purchaser with copies of all written notices
delivered or received under the Leases.

                                       21

<PAGE>

          F. Promptly provide Purchaser a copy of any notice of litigation
received by Seller that may materially and adversely affect the ownership or
operation of the Property.

     15. Purchaser's Closing Conditions Precedent. Purchaser's obligation to
consummate the transaction contemplated by this Agreement shall be subject to
satisfaction or waiver of each of the following conditions ("Purchaser's Closing
Conditions Precedent"); provided, however that Purchaser shall have the
unilateral right to waive any Purchaser's Closing Conditions Precedent, in whole
or in part, by written notice to Seller:

          A. The representations of Seller herein shall be, in all material
respects, true and complete as of Settlement.

          B. Seller shall have performed all of the obligations required to be
performed by Seller under this Agreement, as and when required by this
Agreement, in all material respects.

          C. There shall not have been instituted and be pending any action or
proceeding before any court, governmental agency or other regulatory or
administrative agency or commission challenging the purchase and sale of the
Argo Membership Interests or the FLLP Membership Interests or the transactions
related thereto that seeks to restrain, prevent or change the transactions
contemplated hereby or questions the validity of such transactions.

          D. Neither the Purchaser nor the Seller shall have terminated this
Agreement as provided herein.

          E. Purchaser shall have received an estoppel certificate,
substantially in the form attached to the Leases or, if no such form is
attached, in the form of EXHIBIT J attached hereto and made a part hereof, with
such additional information or modifications reasonably approved by Purchaser,
from (i) Tenants under Leases (the "Estoppel Certificates"). Seller and
Purchaser agree that Seller shall not be in default under this Agreement if
Seller is unable to obtain an Estoppel Certificate from one or more of the
Tenants and that no costs, expenses or other damages shall be due to Purchaser
in such event. Seller shall, and shall cause Owner to, use reasonable efforts to
obtain such Estoppel Certificates from each Tenant; provided, however, neither
Seller nor Owner shall be required to expend significant monies or make
significant concessions or institute litigation in order to obtain such Estoppel
Certificates. If Seller has received Estoppel Certificates from Tenants under
Leases constituting at least eighty five percent (85%) of the rentable square
feet of the occupied portion of the Property (which shall include an estoppel
from Nextone irrespective of whether it is then in occupancy), Seller shall be
deemed to have satisfied the condition set forth in this subsection 15E.

          F. The Lease Transactions shall have been consummated.

     16. Business Days. Any date specified in this Agreement which falls on a
Saturday, Sunday or legal holiday in the State of Maryland shall be extended to
the first regular business day after such date which is not a Saturday, Sunday
or legal holiday.

     17. Confidentiality. Between the date of this Agreement and Settlement, the
Purchaser (i) will hold and will use reasonable efforts to cause its officers,
directors, employees, accountants, representatives, agents, consultants, and
advisors (collectively, its

                                       22

<PAGE>

"Representatives") to hold in strict confidence, all information furnished to
the Purchaser or its Representatives by the Seller or its representatives in
connection with the transactions contemplated by this Agreement as well as all
information concerning the Property contained in any analyses, compilations,
studies, or other documents prepared by or on behalf of the Purchaser
(collectively, the "Information"); and (ii) will not, without the prior written
consent of Seller, release or disclose any of the Information to any other
person, except (1) to the Purchaser's Representatives (a) who need to know the
Information in connection with the consummation of the transactions contemplated
by this Agreement, (b) who are informed by the Purchaser of the confidential
nature of the Information, and (c) who agree to be bound by the terms and
conditions of this Section 17 and (2) to the extent required by law (including
disclosure by the Purchaser, as determined in Purchaser's sole discretion, in
any registration statement or other filing with the U.S. Securities and Exchange
Commission). Information shall not include any information which can be shown to
be or have become (A) generally available to the public other than as a result
of a disclosure by the Purchaser or its Representatives or (B) available to the
Purchaser on a non-confidential basis from a source other than Seller or its
agents, provided that such source is entitled to disclose such information.
Except as permitted in this Section 17, neither Purchaser or Seller shall
disclose the terms of this Agreement to any third party. The terms of this
Section 17 shall survive settlement.

     In the event the Purchaser or any person to whom the Purchaser transmits
the Information pursuant to this Agreement becomes legally compelled to disclose
any of the Information prior to Settlement, Purchaser (a) will provide Seller
with prompt notice thereof so that Seller may seek a protective order or another
appropriate remedy and/or waive compliance with the provisions of this Section
17, (b) will furnish only that portion of the Information which the Purchaser is
(as advised by counsel) legally required to disclose, and (c) will cooperate
with Seller in obtaining, at Seller's expense, a protective order or another
reliable assurance that confidential treatment will be accorded to the
Information. If the transactions contemplated by this Agreement are not
consummated, any documents or other materials containing Information will be
returned to the Seller immediately upon the Seller's request therefore.

     18. Montgomery County Disclosures. The following disclosures are made
pursuant to applicable law in Montgomery County, Maryland:

          A. GENERAL/MASTER PLANS. Purchaser acknowledges that Purchaser has
been apprised of Purchaser's rights to review the applicable master plan and the
municipal land use plan and any related amendments, including maps showing
planned land uses, roads and highways, and the location and nature of proposed
parks and other public facilities affecting the Property prior to the execution
of this Agreement. Purchaser acknowledges that Purchaser is aware that the
applicable plan or general plan for Montgomery County is available at the
Maryland National Capital Park and Planning Commission and that at no time did
Seller explain to Purchaser the intent or meaning of such a plan nor did
Purchaser rely on any representations made by Seller pertaining to the
applicable master plan or general plan

          B. NOTICE AND DISCLOSURE OF AVAILABILITY OF SEWAGE DISPOSAL SYSTEM IN
DESIGNATED AREAS.

                                       23

<PAGE>

               (i) Notice is hereby given to Purchaser, pursuant to the
Montgomery County Code, of the obligation of Seller, or Seller's duly authorized
agent, to disclose to Purchaser any information known to Seller as to whether
the Property is connected to, or has been authorized for connection to, a
community sewerage system, and if not, whether an individual sewage disposal
system has been constructed on the Property, or whether the Property has been
disapproved by the county for the installation of any individual sewage disposal
system.

               (ii) If an individual sewage disposal system has been or is to be
installed upon the Property, and if the Property is located in a subdivision,
and if Purchaser received a copy of the subdivision record plat, as provided
above, Purchaser indicates that Purchaser has reviewed the said record plat,
including any provisions thereon with regard to areas restricted for the initial
and reserve well locations and the individual sewer disposal systems, and the
restricted area in which construction of the building to be served by the
individual sewage disposal system is permitted.

          C. MASTER PLAN AND MUNICIPAL LAND USE PLAN. By signing this Agreement,
Purchaser hereby acknowledges: (1) Seller has offered Purchaser the opportunity
to review the applicable master plan and municipal land use plan and any adopted
amendment; (2) Seller has informed Purchaser that amendments affecting the plan
may be pending before the planning board or the county council or a municipal
planning body; (3) (a) Purchaser has reviewed each plan and adopted amendment,
or (b) Purchaser has waived the right to review each plan and adopted amendment;
and (4) Purchaser understands that, to stay informed of future changes in county
and municipal land use plans, the Purchaser should consult the planning board
and the appropriate municipal planning body.

     19. Miscellaneous.

          A. NOTICES. Any and all notices, requests, consents, approvals or
other communications hereunder shall be deemed to have been duly given only if
in writing and if transmitted by hand delivery with receipt therefor, by
recognized overnight courier, or by registered or certified mail, return receipt
requested, first-class postage prepaid addressed as follows (or to such new
address as the addressee of such a communication may have notified the sender
thereof):

               To Seller:       c/o Argo Investment Company, LC
                                9600 Rockwell Road
                                Suite 200
                                Rockville, Maryland 20850
                                Attn: Mr. Richard L. Perlmutter
                                Facsimile: (240) 499-9686

               With copy to:    J. Richard Saas, Esq.
                                Tenenbaum & Saas, P.C.
                                4504 Walsh Street
                                Suite 200
                                Chevy Chase, Maryland 20815
                                Facsimile: (301) 961-5305

                                       24

<PAGE>

               To Purchaser:    Columbia Equity Trust, Inc.
                                1750 H Street, NW
                                Suite 500
                                Washington, DC 20006
                                Attn: Mr. Oliver T. Carr, III
                                Facsimile: (202) 303-3088

               With copy to:    John M. Ratino, Esq.
                                Hunton & Williams LLP
                                1900 K Street, NW
                                Washington, DC 20006
                                Facsimile: (202) 778-2201

               To Escrow Agent: LandAmerica Commercial Services
                                1015 15th Street, NW
                                Suite 300
                                Washington, DC 20005
                                Attn: Sarah (Sally) Eckert Webb
                                Facsimile: (202) 737-4108

          B. GOVERNING LAW. This Agreement shall be construed and enforced in
accordance with the laws of the State of Maryland, without regard to choice of
law principles.

          C. HEADINGS. The captions and headings herein are for convenience and
reference only and in no way define or limit the scope or content of this
Agreement or in any way affect its provisions.

          D. EFFECTIVE DATE. This Agreement shall be effective as of the date of
full and final execution and delivery hereof by Purchaser and Seller. The term
"Effective Date" means the latest of the dates set forth after the signatures on
behalf of Seller and Purchaser on the signature page of this Agreement.

          E. COUNTERPART COPIES. This Agreement may be executed in two or more
counterpart copies, all of which counterparts shall have the same force and
effect as if all parties hereto had executed a single copy of this Agreement.

          F. BINDING EFFECT; ASSIGNMENT. This Agreement shall be binding upon,
and inure to the benefit of, the parties hereto and their respective successors
and assigns; provided, however, that Purchaser shall not be entitled to assign
this Agreement without the prior written consent of Seller, which consent shall
be given or withheld at Seller's sole discretion; provided, however, that
Purchaser shall be entitled to assign its rights under this Agreement without
Seller's consent (but with not less than 10 days prior written notice to Seller,
which notice shall include a copy of the proposed written assignment) at and as
of the Settlement Date (but not prior thereto) to an entity in which Purchaser
or Columbia Equity, LP, directly or indirectly, is the equity owner (a
"Purchaser Affiliate"), provided that such assignment shall not release
Purchaser of or from its obligations hereunder. Purchaser shall have the right
to designate any

                                       25

<PAGE>

Purchaser Affiliate as the party to receive and assume the Argo Membership
Interests and the FLLP Membership Interests at Settlement.

          G. ENTIRE AGREEMENT. This Agreement and the Exhibits attached hereto
contain the final and entire agreement between the parties hereto with respect
to the sale and purchase of the Property and are intended to be an integration
of all prior negotiations and understandings. Purchaser and its agents, and
Seller and its agents, shall not be bound by any terms, conditions, statements,
warranties or representations, oral or written, not contained herein. No change
or modifications to this Agreement shall be valid unless the same is in writing
and signed by the parties hereto. No waiver of any of the provisions of this
Agreement shall be valid unless the same is in writing and is signed by the
party against with which it is sought to be enforced.

          H. RATIFICATION. Each party shall have three (3) days from the date of
execution by the other to ratify this Agreement and deliver a copy of same to
the other after which time without ratification the offer encompassed herein
shall be null and void.

          I. RISK OF LOSS. The risk of loss to the Property shall remain with
Seller and shall pass to Purchaser simultaneously with delivery of a deed to the
Property to Purchaser.

          J. SURVIVAL. The terms and provisions of this Agreement shall survive
Settlement and delivery of a deed, and shall not be merged therein.

          K. EXHIBITS.

               A    Land

               B    Personal Property

               C    List of Contracts

               D    List of Leases

               E    Information

               F    Rent Roll

               G    Insurance

               H    Banking Relationships

               I    Nextone Lease Terms

               J    Form of Estoppel Certificate

               K    Limited Partnership Agreement of Foulger

               L.   Tenancy in Common Agreement

               M.   Operating Agreement of Argo

               N.   Lender's Escrow Accounts

          L. RECORDATION. Neither this Agreement nor any memorandum or other
summary of this Agreement shall be placed of public record except with the prior
written consent of the Seller and the Purchaser.

          M. TAX DEFERRED EXCHANGE. The Seller shall have the right to structure
the transaction specified herein as a like-kind exchange under Section 1031 of
the Internal Revenue Code ("Section 1031") by providing written notice to
Purchaser at least five (5) days prior to

                                       26

<PAGE>

Settlement, provided that such structuring of the transaction shall not delay
Settlement. In the event the Seller elects to exercise its rights under this
section, then Settlement shall occur in accordance with the terms hereof except
that Seller and an accommodation party (the "Accommodator") permitted by the
regulations promulgated under Section 1031 shall, at Settlement, execute a
mutually acceptable escrow agreement dealing with the retention of the Purchase
Price by the Accommodator and the acquisition of exchange property by the
Accommodator that Seller will receive pursuant to the escrow.

     In the event that Seller elects to exercise its rights to structure this
transaction as a like-kind exchange under Section 1031, the Purchaser agrees to
cooperate with Seller so long as (i) there is no additional financial or other
liability or expense imposed upon the Purchaser, (ii) the rights of Purchaser
are not affected thereby, and (iii) Purchaser has no obligation to acquire land
or property used in such like-kind exchange.

          N. EXCULPATION. Purchaser agrees to look solely to the Seller's
interest in the Owner and the Owner's interest in the Property and, subject to
the limitation set forth in Section 11 hereof, a portion of the proceeds
therefrom, in connection with any recourse against any Seller arising pursuant
to this Agreement. Seller agrees to maintain the legal existence of FLLP, and
the Argo Sellers with an aggregate net worth of at least Two Million Dollars
($2,000,000) for at least one (1) year after Settlement. Purchaser agrees that
no adviser, member, shareholder, trustee, director, officer, partner, employee,
affiliate or subsidiary of any Seller, and no adviser, partner, shareholder,
trustee, director, officer, employee, affiliate or subsidiary of any of the
foregoing shall have any liability under or with respect to this Agreement
solely as a result of such relationship.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement or have
caused this Agreement to be executed on their behalf, under seal, on the date or
dates set forth below.

WITNESS:                                SELLER:

                                        Foulger Land Limited Partnership,
                                        a Virginia limited partnership

                                        By: Sid Foulger (Orchard Ridge), Inc.,
                                            a Maryland corporation,
                                            its General Partner

                                        By:
-------------------------------------       ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------

                                        Argo Orchard Ridge, LC,
                                        a Maryland limited liability company

                                       27

<PAGE>

                                        By: Argo Orchard Ridge Manager, Inc.,
                                            a Maryland corporation,
                                            its Managing Member

                                        By: /s/ John Austin
-------------------------------------       ------------------------------------
                                        Name: John Austin
                                        Title: Member

                                        PURCHASER:

                                        Columbia Equity Trust, Inc.,
                                        a Maryland corporation

/s/ John Schissel                       By: /s/ Oliver T. Carr, III
-------------------------------------       ------------------------------------
                                        Name: Oliver T. Carr, III
                                        Title: CEO

                                       28

<PAGE>

                                    EXHIBIT E

                                101 ORCHARD RIDGE

              REQUESTED PROPERTY DATA (TO THE EXTENT IN SELLERS' OR
                         OWNERS' POSSESSION OR CONTROL)

     1. Basic property description with detail on systems, structure and site;
RECEIVED

     2. Reduced (8-1/2 x 11) floor plans and current site plan;

     3. Most recent ALTA survey; RECEIVED

     4. Quince Orchard Park covenants, easements and restrictions and owner's
association agreements;

     5. All executed leases and subleases (with amendments thereto) regarding
all space occupied by tenants at the Property; RECEIVED

     6. Copies of the tax and utility bills for the Property for calendar years
2004, 2005, and 2006 YTD; RECEIVED

     7. Operating statements (including operating expense information) prepared
by the property manager for the calendar years 2004, 2005 and 2006 YTD; RECEIVED

     8. Capital expenditure program details for 2003, 2004, 2005 and 2006,
including any vendor studies/bids (systems, fire/life safety, structure, ADA);
RECEIVED (GL ONLY; NO DETAIL)

     9. The most recent environmental site assessment report and any soils
reports; RECEIVED PREVIOUS PHASE I

     10. Construction and Design Documents: Base Building Documents (as-built
plans and specifications) plus any revisions, Tenant Improvement Plans, Public
Space Finish Specifications (if different from Base Building Plans), Close out
Manual for each TI project, CADD drawings on disk, documentation and plans for
any subsequent renovations to the base building;

     11. Property Management: Control system plans as built and instructions;

     12. Mechanical operation and maintenance logs in Sellers possession;

     13. Copies of all warranties and warranty information; ROOF WARRANTY
RECEIVED

     14. Certificate of occupancy/non-Residential Use Permits for the Property
and all Tenant space therein; RECEIVED

     15. Seller's operating budget for the Property for 2006; RECEIVED

     16. A current rent roll for the Property in the form currently maintained
by Seller; RECEIVED

     17. List of all security deposits/letters of credit/tenant financial
statements provided to Seller or Lender; RECEIVED CALCULATION OF SECURITY
DEPOSITS HELD

<PAGE>

     18. List of all rent abatements, outstanding leasing commissions and
Landlord payments to the Tenants (including but not limited to tenant
improvement allowances and architectural fees for test fits);

     19. UBS loan documents; RECEIVED

     20. Evidence of insurance delivered by the Tenants as required under the
Leases; RECEIVED

     21. A list of all mechanical equipment and service agreements including
service, maintenance, equipment and/or supply contracts, and amendments thereto;

     22. Copies of any audits of reimbursable expenses reconciliations for 2004,
2005 and 2006 (if prepared); 2006 WILL NOT BE COMPLETED UNTIL APRIL

     23. Month-by-month Account Receivables delinquency/aging report for
trailing 12 months; RECEIVED and

     24. Seller's architect's schedule and plans to support the rentable square
footage and gross building area calculations using the current BOMA method of
measurement, to the extent the same is in Seller's possession.

                                      E-30

<PAGE>

                                    EXHIBIT I

                                101 ORCHARD RIDGE

Nextone Lease - Suite 300: Size - 26,743 SF; Maturity Date - 10 years from
execution; Base Rent - $29.83/SF (as of 6/1/06); Escalation - 3% per annum w/
June 1 escalation date.

Harvey Cleary - Suite 350: Size - 8,012 SF; Maturity Date - July 2008; Base Rent
- $26.74/SF (as of 6/1/06); Escalation - 3% per annum w/ Aug. 1 escalation date.

                                      E-31

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