<PAGE>

                             OFFICE LEASE AGREEMENT

                                     between

                           BUILDING IV ASSOCIATES L.P.
                         a Virginia limited partnership
                                  ("LANDLORD")

                                       and

                       PERFORMANCE ENGINEERING CORPORATION
                             a Virginia corporation
                                   ("TENANT")


<PAGE>

                             OFFICE LEASE AGREEMENT

         THIS OFFICE LEASE AGREEMENT (this "LEASE") is made and entered into
this ____ day of ____________, 1999 (the "EFFECTIVE DATE"), by and between
BUILDING IV ASSOCIATES L.P., a Virginia limited partnership ("LANDLORD") and
PERFORMANCE ENGINEERING CORPORATION, a Virginia corporation ("TENANT"), upon all
terms set forth in this Lease and in all Exhibits hereto, to each and all of
which terms Landlord and Tenant hereby mutually agrees, and in consideration of
One Dollar and other valuable considerations, the receipt and sufficiency of
which are hereby acknowledged, and of the rents, agreements and benefits flowing
between the parties hereto, as follows:


                                    ARTICLE 1
                 BASIC LEASE INFORMATION AND CERTAIN DEFINITIONS

         SECTION 1.01. Each reference to this Lease to information and
definitions contained in Article 1 and each use of the terms capitalized and
defined in this SECTION 1.01 shall be deemed to refer to, and shall have the
following meanings:

         A.       Building:         Fair Lakes Four
                                    12700 Fair Lakes Circle
                                    Fairfax, Virginia 22033

         B.       Premises: The Premises located on the entire second (2nd)
                  floor of the Building, as more fully described and shown on
                  the floor plan attached as EXHIBIT "A".

         C.       Term:  Approximately thirteen (13) years and nine (9) months.

         D.       Commencement Date:  As defined in SECTION 1.01 of EXHIBIT "C".

         E.       Expiration Date:  December 31, 2013

         F.       Rentable Area of the Building:  75,044 square feet.

         G.       Rentable Area of the Premises:  21,000 square feet.

         H.       Tenant's Proportionate Share:  27.98%.

         I.       Base Rent:  As defined in SECTION 3.01 of EXHIBIT "C".

         J.       Security Deposit:  $84,875.00, as adjusted pursuant to ARTICLE
                  23 of EXHIBIT "C".

         K.       Adjustment Factor:  3.5%

         L.       Landlord's Address for Notices:

                           c/o The Peterson Companies
                           12500 Fair Lakes Circle
                           Suite 400
                           Fairfax, Virginia 22033
                           Attention:  Asset Manager

         M.       Tenant's Address for Notices:

                           Performance Engineering Corporation
                           12750 Fair Lakes Circle
                           Fairfax, Virginia 22033
                           Attention:  David Karlgaard


                                                                               2
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

         N.       Lease: Collectively refers to this Office Lease Agreement
                  together with the following Exhibits which are attached
                  hereto and incorporated herein by this reference.

                           EXHIBITS

                           "A" -- Floor Plans
                           "B" -- Leasehold Improvements
                           "C" -- General Lease Provisions
                           "D" -- Rules and Regulations
                           "E" -- Right of First Refusal and Offer Letter
                           "F" -- Nondisturbance, Subordination and Attornment
                                  Agreement

         O.       Broker:  CB Commercial


                                    ARTICLE 2
                                 DEMISE AND TERM

         Landlord leases to Tenant, and Tenant leases from Landlord, the
Premises located in the Building for the Term and subject to the provisions
hereof. The Term of this Lease shall be for the period specified in SECTION 1.01
and shall begin at midnight on the Commencement Date (as defined in the General
Lease Provisions) and shall, unless this Lease is sooner terminated in
accordance with the provisions of this Lease, end at midnight on the Expiration
Date, provided, however, that if for any reason the Expiration Date shall be a
day other than the final day of a calendar month then, the Term of this Lease
shall be extended so that it will expire on the last day of the calendar month
in which the Expiration Date takes place.


                                    ARTICLE 3
                                 RENEWAL OPTION

         Tenant shall have the right to renew and extend the Term of this Lease
with respect to the entire Premises then subject to this Lease for the Renewal
Term (herein so called) upon and subject to the following terms and conditions:

         1. Tenant may extend this Lease for two (2) Renewal Terms of five (5)
years each by giving written notice thereof to Landlord no later than (i) twelve
(12) months prior to the expiration of the original Term with respect to the
first Renewal Term and (ii) twelve (12) months prior to the expiration of the
first Renewal Term with respect to the second Renewal Term. Landlord, at its
sole option, shall have the right to shorten the notice period required for
Tenant's exercise of its renewal options hereunder from twelve (12) months to
some shorter period of time by providing written notice to Tenant of Landlord's
consent to the shorter notice period; however, consent to a shorter notice
period with respect to the first Renewal Term shall not be deemed consent by
Landlord to a shorter notice period with respect to the second Renewal Term. The
first Renewal Term shall commence immediately upon the expiration of the
original Term and the second Renewal Term shall commence immediately upon the
expiration of the first Renewal Term. Upon exercise by Tenant of its right to a
Renewal Term, the Expiration Date of the Term shall automatically become the
last day of the Renewal Term. If Tenant does not exercise its rights to a
Renewal Term in a timely manner, Tenant's failure shall conclusively be deemed a
waiver of its rights to such Renewal Term and all future Renewal Terms.

         2. The exercise by Tenant of its rights to a Renewal Term must be made,
if at all, by written notice executed by Tenant and delivered to Landlord on or
before the date set forth above. Once Tenant shall exercise its rights to a
Renewal Term, Tenant may not thereafter revoke such exercise. Tenant shall not
have the right to exercise a Renewal Term if Tenant is in monetary or material
non-monetary Default under this Lease, either at the time Tenant gives notice of
its election or immediately prior to the commencement of the Renewal Term.


                                                                               3
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

         3. Tenant shall take the Premises "as is" for the Renewal Term and
Landlord shall have no obligation to make any improvements or alterations to the
Premises.

         4. Base Rent per square foot of Rentable Area of the Premises for the
first year of the Renewal Term shall be the sum of the following: (i) the
adjusted Net Base Rent in effect immediately prior to the expiration of the
original Term, with respect to the first Renewal Term, and the expiration of the
first Renewal Term, with respect to the second Renewal Term, shall be multiplied
by the Adjustment Factor and the amount computed shall be added to the adjusted
Net Base Rent in effect immediately prior to the expiration of the original
Term, with respect to the first Renewal Term, and the expiration of the first
Renewal Term, with respect to the second Renewal Term and (ii) the total
commissions paid with respect to Tenant's lease of the Premises during the
Renewal Term(s) amortized over the respective Renewal Term(s) at nine and
one-half percent (9.5%) per annum. During each year of the Renewal(s), Base Rent
shall be increased annually on the anniversary of the Commencement Date by the
Adjustment Factor.

         5. Subject to SUBPARAGRAPH 4 above, the leasing of the Premises for the
Renewal Term shall be upon the same terms and conditions as are applicable for
the original Term, and shall be upon and subject to all of the provisions of
this Lease, including, without limitation, the obligation of Tenant to pay
Tenant's Additional Rent under the Lease.


                                    ARTICLE 4
                              INTENTIONALLY OMITTED


                                    ARTICLE 5
                              INTENTIONALLY OMITTED


                                    ARTICLE 6
                              INTENTIONALLY OMITTED


                                    ARTICLE 7
                 RIGHT OF FIRST OFFER AND RIGHT OF FIRST REFUSAL

         Tenant's rights and obligations with regard to the Right of First Offer
and the Right of First Refusal as described and agreed to by letter dated April
7, 1998 from Landlord to Tenant, a copy of which is attached hereto as EXHIBIT
"E", are incorporated herein by this reference, except that the following
changes shall be incorporated:

                  1.       In paragraph 1(a), change the first sentence to read:

                                    "If at any time during the Offer Period,
the Fair Lakes IV Landlord is prepared AND ABLE to offer to a third party in the
open market any space in Fair Lakes IV THAT WILL BE AVAILABLE TO LEASE, then the
Fair Lakes IV Landlord shall send a written offer notice (the "OFFER NOTICE") to
Tenant of such intent to lease."

                  2. Paragraph 1(d) shall be changed to read as follows:

                                    "Should Tenant either fail to respond within
the five (5) business day period, or elects not to accept the Offer Notice, then
Landlord shall have the right to offer for lease such Offered Space to any other
third parties. However, Landlord shall not have the right to actually lease such
Offered Space to a third party until Landlord provides Tenant, and Tenant elects
not to accept, its Right of First Refusal option as described in Paragraph 2
below."

                  3. At the beginning of the first paragraph under Part 2 -
Right of First Refusal; Fair Lakes IV, insert the following sentence:


                                                                               4
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

                                    "Provided  Landlord has previously offered
to Tenant, and Tenant has elected not to accept, a Right of First Offer Notice
pursuant to Paragraph 1 above for the space in question, Tenant shall have a
Right of First Refusal option as further described below."

                  4. Throughout Paragraph 2, the term "Offer Notice" shall be
changed to "Refusal Notice".


                                    ARTICLE 8
                          TENANT IMPROVEMENT ALLOWANCE

         Landlord shall provide Tenant with an allowance (the "TENANT
IMPROVEMENT ALLOWANCE") for the construction of leasehold improvements to the
Premises of up to $8.00 per square foot of Rentable Area comprising the
Premises, but in no event to exceed $168,000.00. The Tenant Improvement
Allowance shall be applied by Landlord to the costs to be borne by Tenant
pursuant to EXHIBIT "B" to the Lease. Tenant shall reimburse Landlord for all
amounts paid by Landlord to Tenant from the Tenant Improvement Allowance on a
monthly basis with Tenant's payment of Base Rent in an amount equal to the
Tenant Improvement Allowance Rate. The Tenant Improvement Allowance Rate shall
mean the Tenant Improvement Allowance provided by Landlord to Tenant amortized
over the remaining Term at an interest rate of nine and one-half percent (9
1/2%) per annum. The Tenant Improvement Allowance Rate shall constitute
Additional Rent due under the Lease with Tenant's payment of Base Rent.


                                    ARTICLE 9
                            GENERAL LEASE PROVISIONS

         As set forth in SECTION 1.01 of the Office Lease Agreement, this Lease
includes and incorporates the General Lease Provisions attached hereto as
EXHIBIT "C". As more fully set forth in the General Lease Provisions, this Lease
sets forth the entire agreement between Landlord and Tenant relating to the
Premises and the Building. The parts of this Lease which are written, printed,
or typewritten shall have no greater force or effect than and shall not control
over other parts of the Lease, but all parts shall be given equal effect.


                                                                               5
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

         WITNESS the following signatures and seals of Landlord and Tenant made
as of the date first above written.

                                            LANDLORD:

                                            BUILDING IV ASSOCIATES L.P.
                                            a Virginia limited partnership

                                            By:     Building IV Associates, Inc.
                                                    a Virginia corporation
                                                    its general partner

                                            By:
                                                    ---------------------------
                                            Name:
                                                    ---------------------------
                                            Its:
                                                    ---------------------------


                                            TENANT:

                                            PERFORMANCE ENGINEERING
                                            CORPORATION
                                            a Virginia corporation

                                            By:
                                                    ---------------------------
                                            Name:
                                                    ---------------------------
                                            Its:
                                                    ---------------------------


                                                                               6
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

                              EXHIBIT "A" TO LEASE


                          Floor Plan(s) of the Premises


                         Fair Lakes Four Office Building
                                  Second Floor

                                [GRAPHIC OMITTED]


                                                                             A-1
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

                              EXHIBIT "B" TO LEASE

                                     Between

                           BUILDING IV ASSOCIATES L.P.
                                  ("LANDLORD")

                                       and

                       PERFORMANCE ENGINEERING CORPORATION
                                   ("TENANT")


                             LEASEHOLD IMPROVEMENTS

         This EXHIBIT "B" is attached to and made a part of that certain Office
Lease Agreement dated _____________, 19___ (the "LEASE"), between BUILDING IV
ASSOCIATES L.P. ("Landlord"), and PERFORMANCE ENGINEERING CORPORATION,
("TENANT"). The terms used in this Exhibit that are defined in the Lease shall
have the same meanings as provided in the Lease.

         The purpose of this EXHIBIT "B" is to set forth the relative rights and
obligations of Landlord and Tenant with respect to the construction and
installation of the initial tenant improvements.

A.       DEFINITIONS

         1. "BUILDING STANDARD" means the allowances, materials, finishes and
design services required by Landlord for the Building as specified on SCHEDULE 1
attached hereto and incorporated herein.

         2. "NON-BUILDING STANDARD" means all materials, finishes, and design
services used in connection with the construction and installation of the
Leasehold Improvements which exceed Building Standard allowances or deviate from
Building Standard specifications.

         3. "LANDLORD'S CONTRACTOR" means the person or firm from time to time
selected by Landlord to construct and install the Leasehold Improvements in the
Premises.

         4. "LEASEHOLD IMPROVEMENTS" shall mean the aggregate of Building
Standard and Non-Building Standard work in the Premises required by the Approved
Plan.

         5. "LANDLORD'S ARCHITECT" shall mean the architect or space planner
engaged by Landlord to prepare the plans and specifications for the Leasehold
Improvements.

         6. "APPROVED PLAN" shall mean the plan for Leasehold Improvements
approved by Landlord and Tenant pursuant to PARAGRAPH D.4. hereof.

B.       GENERAL PROVISIONS

         1. Unless otherwise agreed to in writing by Landlord and Tenant, all
work involved in the design and construction of the Leasehold Improvements shall
be carried out by Landlord's Architect, and Landlord's Contractor under the sole
direction of Landlord. Tenant shall cooperate with Landlord, Landlord's
Contractor, and Landlord's Architect to promote the efficient and expeditious
completion of such work so that occupancy of the Premises may occur on the
Commencement Date.

         2. On or before the Commencement Date, Landlord shall use its best
efforts to substantially complete the Leasehold Improvements which are to be
constructed or installed by Landlord in the Premises pursuant to the Approved
Plan.


                                                                             B-1
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

         3. If the cost to construct the Leasehold Improvements exceeds the
Tenant Allowances stipulated in the Lease, Landlord shall have no obligation to
commence installation of any Leasehold Improvements in the Premises or continue
construction of the Leasehold Improvements until Landlord receives Tenant's
advance payment as described in this Exhibit. Tenant agrees that in the event of
default of payment thereof, Landlord (in addition to other remedies) shall have
the same rights as in the Event of Default of payment of Rent under the Lease
and all delays in the completion of the Leasehold Improvements resulting from
Tenant's non-payment of such deficiency shall constitute Tenant Delay.

C.       DESIGN

         1. Tenant shall devote such time in consultation with Landlord's
Architect as necessary to enable Landlord's Architect to develop Tenant's
complete working drawings and specifications of the Leasehold Improvements.
Landlord shall pay for the cost of design services (including all necessary
architectural, mechanical and electrical drawings) required for the Approved
Plan.

         2. All design, construction and installation shall conform to the
requirements of applicable building, plumbing and electrical codes and the
requirements of any authority having jurisdiction over, or with respect to, such
work.

         3. All architectural, mechanical and electrical plans and
specifications must be approved by Landlord. Any changes in the Approved Plan
must also be approved by Landlord. Tenant shall not be permitted to modify the
Building in any way, including but not limited to the structural, mechanical and
electrical systems, except as approved by Landlord on the Approved Plan. No
alterations by Tenant to the Leasehold Improvements shall be allowed at any time
except as provided in the Lease.

D.       PROCEDURES FOR COMPLETION OF LEASEHOLD IMPROVEMENTS

         The following procedures shall be followed in completing the Leasehold
Improvements.

         1. As soon as reasonably practical after the execution of the Lease,
Tenant shall meet the Landlord's Architect and provide information for design of
a space plan for the Premises.

         2. Landlord's Architect shall complete the space plan and submit the
same to Tenant and Landlord approval. Within five (5) business days after
Tenant's receipt of such space plan, Tenant shall notify Landlord whether Tenant
approves or disapproves the same.

         3. Upon approval of the space plan by Tenant, Landlord shall cause a
preliminary budget to be prepared indicating the estimated total design and
construction costs to construct the space plan. The budget will indicate the
estimated costs to be borne by both Landlord and Tenant, pursuant to the
allowances set forth in this Lease. Tenant acknowledges that the budget is
merely an estimate of the anticipated costs to improve the Premises generally in
accordance with the space plan, and that the budget is subject to change pending
completion of all design and construction work.

         4. Upon approval of the space plan and budget by Tenant and Landlord,
Landlord's Architect shall be authorized to complete architectural, mechanical,
and electrical working drawings and specifications. Tenant shall provide
Landlord's Architect with any additional information needed for completion of
the working drawings.

         5. Landlord's Architect shall complete working drawings and
specifications and submit the same to Tenant and Landlord for approval. Within
five (5) business days after Tenant's receipt of such working drawings and
specifications, Tenant shall notify Landlord in writing as to whether Tenant
approves or disapproves such working drawings and specifications.

         6. Upon approval of working drawings by Tenant and Landlord, Landlord
shall, within a reasonable period, have the working drawings bid by several
contractors approved by Landlord. Landlord will submit the construction pricing
along with all other estimated costs for design, engineering, permits and
Landlord's construction management fees (not to exceed five percent


                                                                             B-2
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

(5%)) to Tenant for Tenant's approval, indicating the estimated costs, if any,
to be borne by Tenant. Within five (5) business days after Tenant's receipt of
Landlord's price, Tenant shall notify Landlord in writing as to whether Tenant
approves or disapproves of Landlord's price. If Tenant fails to notify Landlord
within such five (5) day period, Tenant shall be deemed to have approved
Landlord's prices. Tenant's signature on the working drawings, plans and
specifications shall acknowledge Tenant's full acceptance of the working
drawings, plans and specifications and Tenant's binding obligation to pay for
all items shown on or in the same as priced by Landlord. Tenant's failure to
sign the working drawings, plans and specifications within the five (5) business
day period provided for herein shall be deemed a "TENANT DELAY" pursuant to
PARAGRAPH F below. Upon approval of working drawings and specifications by
Tenant and Landlord such drawings and specifications shall be the Approved Plan.

         7. Any costs to be borne by Tenant shall be paid by Tenant to Landlord
as follows:

                  (a) 50% of Tenant's costs shall be paid prior to the
commencement of construction.

                  (b) 50% of Tenant's costs shall be paid prior to the
Commencement Date or occupancy.

         8. Landlord and Landlord's Contractor shall seek all necessary permits
for construction of the Leasehold Improvements. As soon as the permits required
for construction have been obtained, Landlord shall authorize Landlord's
Contractor to commence construction of Leasehold Improvements.

         9. In the event Tenant desires to make any changes or revisions to the
Approved Plan, then any delay in the furnishing, delivery or installation of any
such changed items, including all delays in the revision or working drawings and
specifications, shall be deemed Tenant Delay. The cost of such changes,
including any changes by the Landlord's Architect or Contractor, shall be due
from Tenant upon the submission of pricing for such changed items.

E.       DELIVERY OF PREMISES

         1. Tenant is permitted to make periodic inspections of the Premises
during construction provided that such inspections are made during reasonable
business hours and Tenant is accompanied by a representative of Landlord. If
Tenant enters the Building or Premises without being accompanied by a
representative of Landlord, Tenant shall be deemed to be trespassing upon the
Building or the Premises and Landlord shall not be liable for any damage or
injury sustained by Tenant, or any of Tenant's agents, representatives or
employees arising from Tenant's unauthorized entry upon the Building or the
Premises.

         2. Prior to delivery of possession of the Premises to Tenant or
acceptance of the Premises by Tenant, a final inspection of the Premises shall
be made by Tenant, Landlord, Landlord's Architect, and Landlord's Contractor to
make certain that construction was accomplished in substantial accordance with
the Approved Plan. A punch-list of items which require completion or correction
shall be prepared as a result of final inspection, if necessary. Landlord's
Architect shall have authority to determine when, in his best judgment,
substantial completion of the Leasehold Improvements has been accomplished.

         3. Tenant shall be given possession of the Premises upon substantial
completion of construction of the Premises, subject to the punch-list items
described above.

         4. Landlord's Contractor shall be responsible for obtaining the final
inspections and all necessary governmental approvals which are required for
lawful occupancy of the Premises, other than the non-residential use permit
which shall be obtained by Landlord.

         5. Nothing contained in this SECTION E shall be deemed to grant Tenant
any authority to direct Landlord's Architect or Landlord's Contractor in the
performance of their duties during the construction of the Premises.


                                                                             B-3
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

                                                                             B-4
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

F.       COMMENCEMENT OF RENT

         At Lease execution Tenant and Landlord recognized a Commencement Date
which allowed for a reasonable amount of time to complete the Leasehold
Improvements in order to provide Tenant with occupancy of the Premises by the
Commencement Date. Tenant's obligation for payment of Rent under this Lease
shall commence on the Commencement Date, unless such date has been changed and
acknowledged in writing by Landlord and Tenant.

         Landlord shall not be responsible for any delays caused by Tenant which
result in delivery of possession of the Premises later than the Commencement
Date nor shall the Commencement Date be modified for such delay. Such delays
include, but are not limited to the following, all such delays being referred to
as "TENANT DELAY":

         1. Tenant's failure to comply with the procedures for completion of the
Leasehold Improvements outlined in this Exhibit on a timely basis;

         2. Tenant's request for changes or modifications to the work after the
development of the Approved Plan;

         3. Late delivery of or inability to obtain materials required for
Non-Building Standard improvements;

         4. Building code problems related to Non-Building Standard design or
construction; and

         5. The performance of any work by any person or entity employed or
retained by Tenant.


                                                                             B-5
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>


                              EXHIBIT "B" TO LEASE

                                   SCHEDULE 1


                       SCHEDULE OF BUILDING STANDARD WORK

                                RE: Fair Lakes IV


         The following shall constitute the general description and minimum
quality of Building Standard Work, which are utilized in the construction of
Leasehold Improvements by Tenant. Tenant, at its sole cost, shall have the
right, after consultation with and reasonable approval of the Landlord, to make
reasonable substitutions for specific items described herein.

A.       PARTITIONS

         1.       Interior partitions will be constructed of 2 1/2" metal studs
                  at 24" on center, from floor slab to the underside of the
                  finished ceiling, with 1/2" gypsum wallboard panels with taped
                  and finished joints prepared for paint.

         2.       Demising and corridor partitions will be constructed of 2 1/2"
                  studs at 24" on center from floor slab to underside of the
                  deck above with 1/2" gypsum wallboard panels insulated with 2
                  1/2" Batt and with taped and finished joints prepared for
                  paint.

B.       DOORS

         1.       Suite Entry Doors shall be single 3'0" x 8'0" solid core,
                  mahogany veneer with building standard finish, and polished
                  stainless steel butt hinges, lever handles, and mortised
                  lockset, keyed to Landlord's master system.

         2.       Tenant Interior Doors shall be 3'0" x 7'0" solid core,
                  painted, with brushed stainless steel lever hardware.

         3. All doors shall have building standard hollow metal frames.

C.       CEILING

         1.       Ceiling will consist of a 2' x 2' suspended system with 5/8"
                  acoustical tile in a Donne Fineline grid. The approximate
                  finished ceiling height is 8'6".

D.       PAINTING

         1.       All partitions, columns and walls will be painted with two
                  coats of flat latex wall paint. Door frames and interior doors
                  will be painted with two coats of semi-gloss enamel. Suite
                  entry doors will be stained and sealed and will match the
                  building standard finish.

E.       FLOORING

         1.       Carpeting shall be a minimum of 30 ounce face weight cut pile
                  in a color chosen by Tenant from the manufacturer's standard
                  pallet and approved by Landlord.

         2.       Vinyl composition tile may be substituted for carpet at
                  selected areas such as work rooms, pantries, supply rooms,
                  etc. Color may be chosen by Tenant from the manufacturer's
                  standard pallet as approved by Landlord.

         3.       Vinyl wall base will be provided in all areas receiving carpet
                  or floor tile. One color may be chosen by Tenant from the
                  manufacturer's standard pallet as approved by Landlord.


                                                                           B-1-1
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

F.       ELECTRICAL

         1.       Lighting Fixtures will be the Building Standard 2' x 4'
                  florescent lights.

         2.       Electric duplex receptacles and light switches will be black
                  with brushed stainless steel or plastic cover plates to match
                  existing.

         3.       Telephone or data outlets will consist of pre-cut openings in
                  the wall with pull strings up to the ceiling. All
                  telephone/data wiring and cover plates are by Tenant's
                  installer and is not considered part of Leasehold
                  Improvements. All telephone/data outlets shall have cover
                  plates.

G.       HEATING, VENTILATING, AIR CONDITIONING

         1.       A variable air volume (VAV) system provides temperature
                  control to all areas of the Building. Conditioning is provided
                  through light troffer air boots or ceiling diffusers.

H.       SPRINKLERS AND FIRE SAFETY

         1.       An Automatic Sprinkler and Fire Alarm System will be provided
                  in accordance with all national and local codes, including
                  required exit and emergency lights, fire horns, fire hose
                  cabinets and wall mounted extinguishers as required by local
                  authorities.
                  All sprinkler heads shall be recessed with white caps.

I.       WINDOW COVERINGS

         1.       The building has been pre-fitted with thin-line horizontal
                  blinds to match the base building color pallet. No other
                  window treatments will be permitted.


                                                                           B-1-2
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>
                              EXHIBIT "C" TO LEASE

                                     Between

                           BUILDING IV ASSOCIATES L.P.
                                  ("LANDLORD")

                                       and

                       PERFORMANCE ENGINEERING CORPORATION
                                   ("TENANT")


                            General Lease Provisions
                                TABLE OF CONTENTS


<TABLE>
<CAPTION>
<S>      <C>                                                                 <C>
PART 1 - DELIVERY OF THE PREMISES TO TENANT; RENTABLE AREA....................1
         Section 1.01.  Commencement Date.....................................1
         Section 1.02.  Delivery of the Premises to Tenant....................1
         Section 1.03.  Rentable Area.........................................1


PART 2 - ACCEPTANCE OF THE PREMISES AND BUILDING BY TENANT....................1


PART 3 - BASE RENT............................................................1
         Section 3.01.  Base Rent.............................................1
         Section 3.02.  Intentionally Omitted.................................2
         Section 3.03.  Payment...............................................2
         Section 3.04.  Acceptance of Rent....................................2
         Section 3.05.  Survival of Rent Obligation...........................2
         Section 3.06.  Late Payment Fee......................................3
         Section 3.07.  Interest on Past Due Rent.............................3


PART 4 - ADDITIONAL RENT......................................................3
         Section 4.01.  Operating Expenses....................................3
         Section 4.02.  Real Estate Taxes.....................................7
         Section 4.03.  Parking...............................................8
         Section 4.04.  Additional Rent Defined...............................8
         Section 4.05.  Rent Defined..........................................8


PART 5 - SERVICES BY LANDLORD.................................................8


PART 6 - UTILITIES............................................................9
         Section 6.01.  Water, Heating, Ventilating and Air
                  Conditioning................................................9
         Section 6.02.  Electricity...........................................9


PART 7 - USE..................................................................10


PART 8 - COMPLIANCE WITH LAWS AND BUILDING REGULATIONS........................10
         Section 8.01.  Compliance with Laws..................................10
         Section 8.02.  Observance of Building's Rules and
                  Regulations.................................................10
         Section 8.03.  Hazardous Materials...................................10
</TABLE>


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<PAGE>

<TABLE>
<CAPTION>
<S>      <C>                                                                 <C>
PART 9 - ALTERATIONS..........................................................11
         Section 9.01.  Approval of Landlord..................................11
         Section 9.02.  Ownership of Improvements to Premises.................12


PART 10 - LIENS...............................................................13


PART 11 - REPAIRS.............................................................13
          Section 11.01.  Tenant's Obligations................................13
          Section 11.02.  Landlord's Obligations..............................13


PART 12 - INSURANCE...........................................................13
          Section 12.01.  Tenant's Insurance..................................13
          Section 12.02.  Insurance Rating....................................14
          Section 12.03.  Waiver of Subrogation...............................14


PART 13 - DAMAGE BY FIRE OR OTHER CASUALTY....................................15
          Section 13.01.  Damage to Premises..................................15
          Section 13.02.  Damage to Building..................................15
          Section 13.03.  Partial Damage......................................15
          Section 13.04.  Damage During Last Year of Term.....................16
          Section 13.05.  No Landlord Liability...............................16
          Section 13.06.  Apportionment of Rent...............................16


PART 14 - CONDEMNATION........................................................16
          Section 14.01.  Entire Building.....................................16
          Section 14.02.  Portion of Building.................................16
          Section 14.03.  Portion of Premises.................................16
          Section 14.04.  Termination of Lease................................17
          Section 14.05.  Landlord's Right to Award...........................17


PART 15 - ASSIGNMENT AND SUBLETTING...........................................17
          Section 15.01.  Rights of Tenant....................................17
          Section 15.02.  Excess Rent.........................................18
          Section 15.03.  Rights of Landlord..................................19
          Section 15.04.  Affiliate Transfer..................................19


PART 16 - INDEMNIFICATION.....................................................19


PART 17 - SURRENDER OF THE PREMISES...........................................20
          Section 17.01.  Condition of Premises...............................20
          Section 17.02.  Tenant Holdover.....................................20


PART 18 - ESTOPPEL CERTIFICATES...............................................20


PART 19 - SUBORDINATION AND ATTORNMENT........................................21
          Section 19.01.  Existing Financings.................................21
          Section 19.02.  Future Financings...................................21
          Section 19.03.  Attornment..........................................21


PART 20 - QUIET ENJOYMENT.....................................................21
</TABLE>


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<PAGE>

<TABLE>
<CAPTION>
<S>      <C>                                                                 <C>
PART 21 - SIGNS; FURNISHINGS; COMMUNICATION EQUIPMENT.........................22
          Section 21.01.  Signs and Advertisements............................22
          Section 21.02.  Furnishings.........................................22
          Section 21.03.  Communications Equipment............................22


PART 22 - DEFAULTS AND REMEDIES...............................................23
          Section 22.01.  Events of Default...................................23
          Section 22.02.  Remedies............................................24
          Section 22.03.  Remedies Cumulative.................................24
          Section 22.04.  No Acceptance or Surrender..........................24
          Section 22.05.  Customs and Practices...............................25
          Section 22.06.  Payment of Tenant's Obligations by Landlord.........25
          Section 22.07.  Default by Landlord.................................25


PART 23 - SECURITY DEPOSIT....................................................25
          Section 23.01.  Application of Security Deposit.....................25
          Section 23.02.  Transfer of Security Deposit........................26
          Section 23.03.  Letter of Credit....................................26
          Section 23.04.  Changes to Security Deposit.........................26


PART 24 - INTENTIONALLY OMITTED...............................................26


PART 25 - ATTORNEYS FEES AND LEGAL EXPENSES...................................26


PART 26 - NOTICES.............................................................26


PART 27 - MISCELLANEOUS.......................................................27
          Section 27.01.  No Partnership......................................27
          Section 27.02.  Brokers.............................................27
          Section 27.03.  Severability........................................27
          Section 27.04.  Trial by Jury.......................................27
          Section 27.05.  Force Majeure.......................................27
          Section 27.06.  Captions............................................28
          Section 27.07.  Benefit and Burden..................................28
          Section 27.08.  No Representations by Landlord......................28
          Section 27.09.  Entire Agreement....................................28
          Section 27.10.  No Offer............................................28
          Section 27.11.  Authority...........................................28
          Section 27.12.  Changes Requested by Lender.........................29
          Section 27.13.  Governing Law and Construction......................29
          Section 27.14.  Landlord's Liability................................29
          Section 27.15.  Use of Name of Building.............................29
          Section 27.16.  Changes by Landlord.................................29
          Section 27.17.  Time of Essence.....................................30
</TABLE>


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<PAGE>



           PART 1 - DELIVERY OF THE PREMISES TO TENANT; RENTABLE AREA

         SECTION 1.01.  COMMENCEMENT DATE.

         The Commencement Date shall be the earlier of Tenant's occupancy or
April 1, 2000; provided, however, that if Tenant will be performing alterations
to the Premises requiring building or other permits, then the Commencement Date
shall be delayed by one-half (1/2) of the number of days that Landlord and
Tenant reasonably anticipate will be required for Tenant to construct such
alterations. In no event, however, shall the Commencement Date be delayed by
more than forty-five (45) days or later than May 15, 2000.


         SECTION 1.02.  DELIVERY OF THE PREMISES TO TENANT.

         Landlord shall deliver possession of the Premises on or before April 1,
2000 broom clean and with all systems and base building improvements in good
working order and in compliance with all applicable laws and ordinances. Tenant
acknowledges and agrees that Tenant is accepting the Premises in its "as is" and
"where is" condition and that Landlord shall have no obligation to perform any
work to the Premises prior to delivery of possession thereof to Tenant subject
to any improvements to be made to the Premises pursuant to ARTICLE 8 and in
accordance with the provisions of EXHIBIT "B" to this Lease.


         SECTION 1.03.  RENTABLE AREA.

         The term "RENTABLE AREA" as used herein means all floor area in the
Building. The Rentable Area of the Premises is stated in the Basic Lease
Information and has been calculated by Landlord's architect ("LANDLORD'S
ARCHITECT") in accordance with Washington, D.C. Association of Realtors modified
method for calculating space in office buildings. The Rentable Area of the
Building and the Premises shall be adjusted, if necessary, by Landlord's
Architect in the event of any future expansion or modification of the Building
and/or the Premises. If the number of square feet of (i) the Rentable Area of
the Building; or (ii) the Rentable Area of the Premises changes, then Tenant's
Proportionate Share shall be adjusted effective as of the date of any such
change.


           PART 2 - ACCEPTANCE OF THE PREMISES AND BUILDING BY TENANT

         Tenant  shall accept the Premises in its "as is" and "where is"
condition and Landlord shall have no obligation to make any improvements to the
Premises prior to the Commencement Date. Taking possession of the Premises by
Tenant shall be conclusive evidence that Tenant: (i) accepts the Premises as
suitable for the purposes for which they are leased; (ii) accepts the Building
and every part and appurtenance thereof as being in a good and satisfactory
condition; and (iii) waives any defects in the Premises or the Building except
for the completion of those items, if any, on Landlord's punch list or latent
defects which cannot reasonably be discovered by an inspection of the Premises
prior to taking possession.


                               PART 3 - BASE RENT

         SECTION 3.01.  BASE RENT.

         Tenant shall pay to Landlord  monthly, in advance, without demand, on
the first day of each calendar month, the monthly Base Rent specified below.
Base Rent shall be calculated on the first day of each Lease Year by multiplying
the Base Rent per Square Foot (as hereinafter defined) by the Rentable Area of
the Premises. The first monthly installment of Base Rent shall be payable in
advance on the Commencement Date. If the Commencement Date is a date other than
the first day of a calendar month, then Tenant shall pay to Landlord on the
Commencement Date a prorated installment of Base Rent for the first fractional
month of the Term. If the Expiration Date is a date


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<PAGE>


other than the last day of a calendar month, then the Term shall be extended to
the last day of such month.

<TABLE>
<CAPTION>
                              Base Rent Per           Net Base Rent
          LEASE YEAR           SQUARE FOOT           PER SQUARE FOOT
          ----------           -----------           ---------------

<S>                                <C>                      <C>
                 1                 $16.32                   $15.41
                 2                 $16.86                   $15.95
                 3                 $17.42                   $16.51
                 4                 $18.00                   $17.09
                 5                 $18.59                   $17.68
                 6                 $19.21                   $18.30
                 7                 $19.86                   $18.95
                 8                 $20.52                   $19.61
                 9                 $21.21                   $20.30
                10                 $21.92                   $21.01
                11                 $22.65                   $21.74
                12                 $23.41                   $22.50
                13                 $24.20                   $23.29
                14                 $25.02                   $24.11
</TABLE>

         For purposes hereof, "Lease Year 1" or the first "Lease Year" shall
mean the period commencing on the Commencement Date and terminating on December
31, 2000. All other references to "Lease Year" shall mean a period of twelve
(12) consecutive months commencing on January 1, 2001, and each successive
twelve (12) month period thereafter.


         SECTION 3.02.  INTENTIONALLY OMITTED.


         SECTION 3.03.  PAYMENT.

         All Base Rent and Additional Rent (as hereinafter defined) shall be
paid to Landlord by Tenant when due, without deduction or offset, in lawful
money of the United States, at Landlord's address for Notice or such other place
as Landlord may from time to time designate in writing.


         SECTION 3.04.  ACCEPTANCE OF RENT.

         If Landlord shall direct Tenant to pay Base Rent and/or Additional Rent
to a lockbox or other depository whereby checks issued in payment of Base Rent
and/or Additional Rent (or both or all, as the case may be) are initially cashed
or deposited by a person or entity other than Landlord (albeit on Landlord's
authority), then, for any and all purposes under this Lease: (i) Landlord shall
not be deemed to have accepted such payment until ten (10) days after the date
on which Landlord shall have actually received such funds, and (ii) Landlord
shall be deemed to have accepted such payment if (and only if) within said ten
(10) day period, Landlord shall not have refunded (or attempted to refund) such
payment to Tenant. Nothing contained in the immediately preceding sentence shall
be construed to place Tenant in default of Tenant's obligation to pay rent if
and for so long as Tenant shall timely pay the rent required pursuant to this
Lease in the manner designated by Landlord.


         SECTION 3.05.  SURVIVAL OF RENT OBLIGATION.

         The obligation of Tenant with respect to the payment of past due Base
Rent and Additional Rent shall survive the termination of this Lease.


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<PAGE>

         SECTION 3.06.  LATE PAYMENT FEE.

         In the event any installment of Rent due hereunder is not paid within
five (5) calendar days after it is due, then Tenant shall also pay to Landlord
as Additional Rent a late payment fee equal to five percent (5%) of such
delinquent installment of Rent or any component thereof for each and every month
or part thereof that such Rent or any component thereof remains unpaid.


         SECTION 3.07.  INTEREST ON PAST DUE RENT.

         All past due installments of Rent shall bear interest until paid at a
rate per annum equal to four percent (4%) above the prime rate of interest from
time to time publicly announced by NationsBank, N.A., or any successor thereof
(the "DEFAULT RATE"); provided, however, that if at the time such interest is
sought to be imposed the rate of interest exceeds the maximum rate permitted
under federal law or under the laws of the Commonwealth of Virginia, the rate of
interest shall be the maximum rate of interest then permitted by applicable law.


                            PART 4 - ADDITIONAL RENT

         SECTION 4.01.  OPERATING EXPENSES.

         (a) Throughout the Term, Tenant shall pay on a monthly basis, without
demand, as Additional Rent for the Premises, Tenant's Proportionate Share of the
Operating Expenses (as defined in SECTION 4.01(b) hereof). Such payments shall
be made as follows:

                  (1) Prior to the Commencement Date and on the first day of
January of each year during the Term, or as soon thereafter as is practicable,
Landlord shall furnish Tenant with Landlord's estimate of the Operating Expenses
for the forthcoming year. On the first day of each month during such year,
Tenant shall pay one-twelfth (1/12th) of Tenant's Proportionate Share of the
estimated Operating Expenses for such year. If for any reason Landlord has not
provided Tenant with Landlord's Operating Expenses estimate on or before the
first day of January of any year during the Term, then, until the first day of
the calendar month following the month in which Tenant is given Landlord's
estimate of Operating Expenses, Tenant shall continue to pay to Landlord on the
first day of each calendar month the monthly sum payable by Tenant under this
SECTION 4.01 for the month of December of the preceding year.

                  (2) On the first day of April of each year during the Term, or
as soon thereafter as reasonably practical, Landlord shall furnish to Tenant a
statement of the actual Operating Expenses for the preceding year. Within thirty
(30) days after the delivery of that statement, a lump sum payment will be made
by Tenant equal to the amount, if any, by which Tenant's Proportionate Share of
the actual Operating Expenses exceeds the amount, if any, which Tenant has paid
toward the estimated Operating Expenses pursuant to SECTION 4.01(a)(1) above. If
Tenant's Proportionate Share of the actual Operating Expenses is less than the
amount Tenant has paid toward the estimated Operating Expenses pursuant to
SECTION 4.01(a)(1) above, Landlord shall apply such amount to the next accruing
installments of Rent due hereunder. The foregoing notwithstanding, Landlord
shall have the right from time to time during any year, but not more frequently
than twice in any calendar year, to notify Tenant in writing of any change in
Landlord's estimate of Operating Expenses for the then current year, in which
event Tenant's Proportionate Share of Operating Expenses, as previously
estimated, shall be adjusted to reflect the amount shown in such notice and
shall be effective, and due from Tenant, on the first day of each month
following Landlord's giving of such notice. Landlord also shall have the right
to bill Tenant for understatements in Operating Expenses charged to Tenant for
only the immediately preceding two (2) calendar years and Tenant shall reimburse
Landlord for such understated charges within thirty (30) days after receipt of
an invoice from Landlord. The effect of this SECTION 4.01(a) is that Tenant will
pay during each year during the Term Tenant's Proportionate Share of actual
Operating Expenses.

                  (3) If the Commencement Date occurs on a date other than the
first day of January, or if the Term ends on a date other than the last day of
December, the actual Operating


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<PAGE>

Expenses for the year in which the Commencement Date or the Expiration Date
occurs, as the case may be, shall be prorated so that Tenant shall pay that
portion of Tenant's Proportionate Share of Operating Expenses for such year
represented by a fraction, the numerator of which shall be the number of days
during such fractional year falling within the Term, and the denominator of
which is 365 (or 366, in the case of a leap year). The provisions of this
SECTION 4.01 shall survive the Expiration Date or any sooner termination
provided for in this Lease.

          (b) As used in this Lease, "OPERATING EXPENSES" means all expenses,
costs, and disbursements of every kind which Landlord incurs, pays or becomes
obligated to pay in connection with the operation, repair, and maintenance of
the Building, which cost shall include all expenditures by Landlord to maintain
all facilities in operation at the beginning of the term and such additional
facilities installed in subsequent years as Landlord may consider necessary or
beneficial for the operation of the Building in a first class manner. All
Operating Expenses shall be determined according to generally accepted
accounting principles (which shall be consistently applied) and shall include,
but are not limited to, the following:

                   (1) Wages, salaries, and fees of all personnel or entities
(exclusive of Landlord's executive personnel) engaged in the operation, repair,
maintenance, or security of the Building, including taxes, insurance and
benefits relating thereto; provided, however, that if such personnel or entities
service other buildings besides the Building, then such wages, salaries and fees
will be prorated to the Building on the basis of (a) the percentage of such
personnel's or entities' time spent servicing the Building, or (b) the square
footage of the buildings serviced (it being understood and agreed that in no
event shall Landlord allocate more than 100% of the compensation and benefits
for any single employee among the properties being serviced by such employee).

                   (2) All supplies and materials used in the operation, repair,
security, and maintenance of the Building;

                   (3) Cost of all maintenance and service agreements for the
Building and the equipment therein, including, without limitation, alarm
service, water treatment services, janitorial services, security systems
service, window cleaning, service on electrical, HVAC and mechanical components,
trash removal, elevator maintenance, extermination service, plumbing service,
grounds keeping, and landscaping;

                   (4) Cost of all insurance relating to the Building for which
Landlord is responsible hereunder, or which Landlord considers reasonably
necessary for the operation of the Building, including, without limitation, the
deductible payments actually made under policies maintained by Landlord, the
cost of property, casualty and liability insurance applicable to the Building
and Landlord's personal property used in connection therewith, and the cost of
business interruption or rental insurance in such amounts as will reimburse
Landlord for all losses of earnings and other income attributable to such perils
as are commonly insured against by prudent landlords or required by Landlord's
lender and the cost of repairs made as a result of damages net of insurance
reimbursement;

                   (5) Cost of repairs and maintenance (excluding repairs and
maintenance paid by proceeds of insurance or by Tenant or other third parties,
and alterations attributable solely to tenants of the Building) of the Building;

                   (6) All utility costs of the  Building (exclusive, however,
of such special utility services as described in PART 6 of the General Lease
Provision, the costs of which special utility services shall be payable as
therein provided), including, without limitation, water, power, fuel, heating,
lighting, air conditioning, and ventilating;

                   (7) Amortization of the cost of installation of capital
investment items which are installed primarily to reduce, and actually does
reduce, operating costs for the general benefit of the Building's tenants or to
maintain and/or repair the Building in first class condition and operation or
which may be required by any governmental authority or regulation. All such
costs shall be amortized at nine percent (9%) per annum over the reasonable life
of the capital investment items, with the reasonable life and amortization
schedule being determined by Landlord, but in no event to extend beyond the
reasonable life of the Building;


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<PAGE>

                   (8) Landlord's central accounting costs, the cost of an
annual audit and Landlord's legal fees relating to the operation of the
Building;

                   (9) A management fee to the manager of the Building whether
or not related to Landlord not to exceed three percent (3%) of gross rents per
year;

                   (10) Building office rent or rental value for any central
Building management office whether in the Building or in another building within
the planned mixed use development known as Fair Lakes (and hereinafter called
the same) provided that if the management office is located in another building
or provides services to buildings in addition to the Building, then only the
Building's pro rata share of rent (based on square footage) shall be included;
and

                   (11) The Fair Lakes League Assessment.

          (c) Notwithstanding any other provision of this Lease, Operating
Expenses (as defined in Section 4.01(b) above), shall not include, and Landlord
shall be solely liable for, the following expenses:

                   (1) Repairs or other work occasioned by insured casualty or
by the exercise of eminent domain, to the extent Landlord is reimbursed by
warranties, service contracts or insurance maintained by Landlord or Tenant
hereof or by the condemning authority;

                   (2) Leasing commissions, attorneys' fees, cost and
disbursements and other expenses incurred in connection with negotiations or
disputes with present or prospective tenants or other occupants of the Building;

                   (3) Costs incurred in improving, decorating, building-out,
painting or redecorating premises for other tenants of the Building;

                   (4) Expenses in connection with services or other benefits of
a type which are not provided Tenant but which are provided to another tenant of
the Building;

                   (5) Costs incurred due to violation by Landlord or any other
tenant of the Building of the terms and conditions of any lease of space in the
Building;

                   (6) Interest or debt or amortization payments on any mortgage
or mortgages;

                   (7) Payments of rent by Landlord to any ground lessor;

                   (8) Landlord's general overhead not related to the operation
of the Building (but without limiting Landlord's right to seek reimbursement as
provided in Sections 4.01(b)(1), (8), (9) and (10) above).

                   (9) Advertising and promotional expenditures with respect to
the Building except for those advertising and promotional expenditures that
directly benefit Tenant;

                   (10) Any costs, fines or penalties incurred due to violations
of any nature by Landlord of any governmental rule or authority;

                   (11) Wages, salaries or other compensation paid to any
executive employees;

                   (12) Rentals and other related expenses incurred in leasing
air-conditioning systems, elevators or other equipment ordinarily considered to
be of a capital nature, except to the extent that (i) Landlord is leasing in
lieu of purchasing such items, if the purchase thereof would be includable in
Operating Expenses, or (ii) rental required on a temporary basis in order for
Landlord to be able to provide services that Landlord is required to provide to
Tenant pursuant to this Lease, if the need therefor was not caused by the
negligence of Landlord or any tenant, or (iii) such expenses are otherwise
properly included under SECTION 4.01(b)(7);



                                                                             C-5
                                      Initials:  _____ (Landlord) _____ (Tenant)
<PAGE>

                   (13) Any cost or expense whatsoever arising from or related
to any clean-up of any hazardous or toxic materials, or any governmental penalty
of fines associated therewith, excepting, however, any such cost or expense
resulting from the negligent or intentional acts of Tenant or its employees,
invitees, guests, agents, representatives, contractors, licensees, successors or
assigns. The term "hazardous or toxic materials" as used in this Lease shall
mean those materials identified in The Comprehensive Environmental Response,
Compensation and Liability Act of 1980 of the United States Code and by the laws
of the Commonwealth of Virginia, as such sections may be amended from time to
time;

                   (14) The cost of excessive use of Building  utilities (such
as HVAC) by other tenants of the Building, and/or utility service by other
tenants outside normal Building hours;

                   (15) Costs incurred in connection with the sale, financing,
refinancing, mortgaging or change of ownership of the Building or the Project,
including without limitation, brokerage commissions, attorneys, and accountants
fees, closing costs, title insurance premiums, transfer taxes and interest
charges;

                   (16) Any and all loss, claim, damage, award, deductibles paid
under any insurance policies or other amount paid or payable by Landlord
(including all attorneys' fees, court costs and other costs incurred in
connection therewith) as a result or arising out of any act of negligence,
breach of contract or willful misconduct by the Landlord or its agents,
employees or contractors to the extent not covered by insurance;

                   (17) Bad debt losses, rent losses or reserves for such
losses; and

                   (18) Non-cash items, such as deductions for depreciation and
amortization of the Building and the Building equipment.

          (d) At Tenant's request, Landlord shall meet with Tenant at a mutually
convenient time to address any questions Tenant may have about particular
Operating Expenses, and Landlord shall provide any such additional backup
documentation as is reasonably requested by Tenant. In the event Tenant does not
contest a statement of Operating Expenses within ninety (90) days after it is
rendered, such statement shall become binding and conclusive; provided, however,
that if a timely audit of Operating Expenses for a particular year reveals an
error resulting in any incorrect charge with regard to particular expenses in
such year, Tenant shall thereupon have the right to re-examine Landlord's books
and records with respect to the immediately preceding two (2) calendar years for
the sole purpose of determining whether the same error resulted in an incorrect
charge with respect to the same expenses in such immediately preceding two (2)
calendar years, and if so, Tenant shall be entitled to a refund of such amount.
In addition, Tenant shall have the right, at Tenant's expense, one time during
each calendar year to examine, to copy and to have an audit conducted of all
books and records of Landlord pertaining to Operating Expenses relating to the
immediately preceding calendar year. If Tenant elects to hire any third party to
assist it with such inspection or audit, such third party must be a certified
public accountant or accounting firm, retained on a non-contingent fee basis
(the "AUDITOR"). Such audit and inspection shall be conducted at a time and
place reasonably acceptable to Landlord and Tenant during normal business hours.
If the amount paid by Tenant to Landlord exceeded the amounts to which Landlord
was entitled hereunder, and if Landlord does not otherwise dispute the results
of the audit as permitted pursuant to the terms hereof, Landlord shall credit
the amount of such excess against the next installment of Rent due and payable
hereunder. If this Lease shall have expired or otherwise terminated, then
Landlord shall refund any overpayment due to Tenant within thirty (30) days
after the amount of the overpayment is determined. In the event that Tenant's
Proportionate Share of Operating Expenses, as calculated by Landlord, exceeds
the correct amount by more than three percent (3%), then Landlord shall promptly
reimburse Tenant for the cost of such audit and inspection. If the amount paid
by Tenant to Landlord is less than the amount Landlord was entitled to
hereunder, Tenant shall make a lump sum payment of the difference between the
amount paid by Tenant and the amount owed to Landlord hereunder within thirty
(30) days after the amount of the underpayment is determined.

          (e) At Tenant's option from time to time, upon forty-five (45) days
prior written notice to Landlord, Tenant may elect to provide or contract
directly for any service otherwise required or permitted to be provided by
Landlord under this Lease (other than management services), and


                                                                             C-6
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<PAGE>

thereafter the cost of providing such service or utility to the Premises and
other tenants of the Building shall not be included for purposes of calculating
Tenant's Proportionate Share of Operating Expenses. If Tenant elects to provide
any service or utility to the Premises, Tenant shall be required to provide such
service or utility in a first-class manner. If Tenant fails to do so, Landlord
shall have the right to commence, once again, providing such service or utility
to the Premises and including the costs thereof in the calculation of Tenant's
Proportionate Share of Operating Expenses. If, after Landlord has transferred
the Building, Fair Lakes IV and Fair Lakes VI to an entity that is not related
in any manner with Landlord, Tenant is leasing one hundred percent (100%) of the
Rentable Area in the Building, Fair Lakes IV and Fair Lakes VI, Tenant
determines in its reasonable discretion that the Building, Fair Lakes IV and
Fair Lakes VI are not being managed in a first-class manner, then Tenant shall
have the right to assume the management responsibilities for the Building,
provided that the Building must be managed in a first-class manner in accordance
with a maintenance and service schedule to be mutually agreed to by Tenant and
Landlord. If Tenant assumes the management of the Building, the management fee
shall not be included for purposes of calculating Tenant's Proportionate Share
of Operating Expenses. If, in Landlord's reasonable discretion, Landlord
determines that Tenant is not managing the Building in a first-class manner,
then Landlord shall, once again, assume the responsibilities for managing the
Building and shall include the management fee for purposes of calculating
Tenant's Proportionate Share of Operating Expenses. Upon sixty (60) days prior
written notice to Landlord, Tenant also may require Landlord to bid out major
contracts for Operating Expenses.


          SECTION 4.02.  REAL ESTATE TAXES.

          (a) Throughout the Term, Tenant shall pay on a monthly basis, without
demand, as Additional Rent for the Premises, Tenant's Proportionate Share of the
actual Real Estate Taxes (as defined in SECTION 4.02(c) hereof). Such payments
shall be made as follows:

                   (1) Prior to the Commencement Date and on the first day of
January of each year during the Term, or as soon thereafter as practicable,
Landlord shall furnish Tenant with Landlord's estimate of the Real Estate Taxes
for the forthcoming year. On the first day of each month during such year,
Tenant shall pay one-twelfth (1/12th) of Tenant's Proportionate Share of the
estimated Real Estate Taxes for such year. If for any reason Landlord has not
provided Tenant with Landlord's estimate of Real Estate Taxes on or before the
first day of January of any year during the Term (or by the Commencement Date,
as the case may be), then until the first day of the calendar month following
the month in which Tenant is given Landlord's estimate of Real Estate Taxes,
Tenant shall continue to pay to Landlord on the first day of each calendar month
the monthly sum payable by Tenant under this SECTION 4.02 for the month of
December of the preceding year.

                   (2) On the first day of April of each year during the Term
or as soon thereafter as reasonably practical, Landlord shall furnish to
Tenant a statement of the actual Real Estate Taxes for the preceding year.
Within thirty (30) days after the delivery of that statement, a lump sum
payment will be made by Tenant equal to the amount, if any, by which Tenant's
Proportionate Share of the actual Real Estate Taxes exceeds the amount, if
any, which Tenant has paid toward the estimated Real Estate Taxes pursuant to
SECTION 4.02(a)(1) above. If Tenant's Proportionate Share of the actual Real
Estate Taxes is less than the amount Tenant has paid toward the estimated
Real Estate Taxes pursuant to SECTION 4.02(a)(1) above, Landlord shall apply
such amount to the next accruing installment(s) of Rent due hereunder. The
foregoing notwithstanding, Landlord shall have the right once the actual Real
Estate Taxes assessment for the applicable year has been received by
Landlord, to notify Tenant in writing of any change in Landlord's estimate of
Real Estate Taxes for the then current year, in which event Tenant's
Proportionate Share of Real Estate Taxes, as previously estimated, shall be
adjusted to reflect the amount shown in such notice and shall be effective,
and due from Tenant, on the first day of each month following Landlord's
giving of such notice. The effect of this SECTION 4.02(a) is that Tenant will
pay during each year during the Term Tenant's Proportionate Share of the
actual Real Estate Taxes in excess of the Base Real Estate Taxes.

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          (b) If the Commencement Date occurs on a date other than the first day
of January, or if the term ends on a date other than the last day of December,
the actual Real Estate Taxes for the year in which the Commencement Date or the
Expiration Date occurs, as the case may be, shall be prorated so that Tenant
shall pay that portion of Tenant's Proportionate Share of Real Estate Taxes for
such year represented by a fraction, the numerator of which shall be the number
of days during such fractional year falling within the Term, and the denominator
of which is 365 (or 366, in the case of a leap year). The provisions of this
SECTION 4.02 shall survive the Expiration Date or any sooner termination
provided for in this Lease.

          (c) As used in this Lease, the term "REAL ESTATE TAXES" shall
including the following:

                   (1) All real estate taxes, including general and special
assessments, if any, which are imposed upon Landlord or assessed against the
Building or the land upon which the Building is situated; and

                   (2) Any other present or future taxes or governmental
charges that are imposed upon Landlord, or assessed against the Building or the
land upon which the Building is situated, including, but not limited to, any tax
levied on or measured by the rents payable by tenants of the Building which is
in the nature of, or in substitution for, real estate taxes. Any inheritance,
estate, gift, franchise, corporation, income, or net profits tax which may be
assessed against Landlord and/or the Building shall be excluded.


          SECTION 4.03.  PARKING.

          During the initial Term and the first Renewal Term, Tenant and its
employees, invitees, and guests shall have the right to use, free of charge, in
common, with the other tenants of the Building, the parking areas for the
Building, all on an unassigned and unreserved basis. Landlord reserves the right
to promulgate reasonable rules and regulations of general application for the
use of all parking spaces.


          SECTION 4.04.  ADDITIONAL RENT DEFINED.

          The term "ADDITIONAL RENT" shall include, but not be limited to (i)
the late payment fee, if any, under SECTION 3.06; (ii) Tenant's Proportionate
Share of Operating Expenses as calculated under SECTION 4.01; (iii) Tenant's
Proportionate Share of Real Estate Taxes as calculated under SECTION 4.02; and
(iv) all other costs and expenses which Tenant assumes, agrees or is required to
pay to Landlord pursuant to this Lease. In the event of nonpayment of Additional
Rent, Landlord shall have all the rights and remedies herein provided for in
case of nonpayment of Rent.


          SECTION 4.05.  RENT DEFINED.

          The term "RENT" shall include Base Rent and Additional Rent.


                          PART 5 - SERVICES BY LANDLORD

          While Tenant is occupying the Premises and is not in Default under
this Lease, Landlord shall furnish the Premises with: (i) passenger elevator
service in common with other tenants for access to and from the Premises,
provided that Landlord may reasonably limit the number of elevators to be
operated at night after normal business hours and on Saturdays, Sundays, and
holidays and that Landlord may remove elevators from service for maintenance;
(ii) janitorial cleaning services Monday through Friday (except holidays) as
required in Landlord's reasonable judgment; (iii) replacement, as necessary, of
all lamps and ballasts in Building Standard light fixtures within the Premises;
and (iv) the utility services provided for in PART 6 below. If Tenant requires
services which are not specified herein and Landlord elects to provide such
services to


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Tenant, Tenant will pay to Landlord, upon demand, as Additional Rent, Landlord's
charges for providing such services.

          Failure to furnish, or any stoppage of, the services provided for in
this PART 5 and in PART 6 below resulting from any cause will not make Landlord
liable in any respect for damages to any person, property, or business, nor be
construed as an eviction of Tenant, nor entitle Tenant to any abatement of Rent,
or damages because of malfunctions or any interruptions in service.

          Notwithstanding the foregoing, if such malfunction or interruption in
service is within Landlord's reasonable control, and such malfunction or
interruption in service (i) continues for three (3) consecutive business days
and (ii) makes it reasonably impossible for Tenant's continued use and occupancy
of the Premises (or portion thereof), and (iii) requires Tenant to vacate the
Premises, then Tenant shall be entitled to an abatement of Base Rent and/or
Adjusted Rent for the portion of the Premises vacated for the period commencing
on the date of the malfunction or interruption of services, and continuing until
the earlier of the following (i) the date such service is corrected or restored
or (ii) the date Tenant reoccupies any part of the Premises which was vacated
because of the interruption in service, notwithstanding the fact that the
malfunction or interruption in service has not been corrected.


                               PART 6 - UTILITIES

          SECTION 6.01.  WATER, HEATING, VENTILATING AND AIR CONDITIONING.

          (a) While Tenant is occupying the Premises and is not in Default under
this Lease, Landlord shall furnish Tenant with the following utilities in the
manner and to the extent customarily provided in office buildings in the
Northern Virginia area: (1) potable water at those points of supply provided
periodically for normal lavatory use by tenants in the Building; (2) heating,
ventilating, and air-conditioning in season on business days from 7:00 a.m. to 6
p.m., and on Saturdays from 8 a.m. to 1 p.m. (except Holidays); and (3) electric
lighting for public areas and special service areas of the Building. For
purposes hereof, "HOLIDAY" shall mean New Year's Day, Memorial Day, Independence
Day, Labor Day, Thanksgiving Day and Christmas Day. If Tenant requires HVAC or
electrical service outside the hours and days specified above, the additional
service may be requested by Tenant and Tenant will pay for such services at the
rate Landlord is then charging therefor, which charge shall be comprised of
actual direct utility costs, maintenance and depreciation costs of equipment and
an administrative cost. Landlord shall have no obligation to provide any
additional service to Tenant at any time Tenant is in Default under this Lease.

          (b) Landlord shall not be liable for its failure to maintain
comfortable atmospheric conditions in all or any portion of the Premises due to
heat generated by any equipment or machinery installed by Tenant (with or
without Landlord's consent) that exceeds generally accepted engineering design
practices for normal office purposes. If Tenant desires additional cooling to
offset excessive heat generated by such equipment or machinery, Landlord will
have the right to install supplemental air conditioning units in the Premises,
and the full cost thereof, including the cost of installation of unit(s) and
meter(s), operation and use, will be paid by Tenant to Landlord on demand.
Tenant will be required to maintain any supplemental air conditioning units
installed pursuant to this Section.


          SECTION 6.02.  ELECTRICITY.

          (a) While Tenant is occupying the Premises and is not in Default under
this Lease, Landlord will furnish sufficient power in the Premises for lighting
and for personal desktop computers, typewriters, word processors, calculating
machines, copying machines, and other similar office equipment of low electrical
consumption. Tenant will not install or operate in the Premises any heavy duty
electrical equipment or machinery without first obtaining prior written consent
of Landlord. Landlord may require, as a condition of its consent, for the
installation of such equipment or machinery, payment by Tenant as Additional
Rent for excess consumption of electricity that may be occasioned by the
operation of said equipment or machinery. Upon


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reasonable prior notice, Landlord may make periodic inspections of the Premises
at reasonable times to determine that Tenant's electrically operated equipment
and machinery complies with the provisions of Part 6.

          (b) If Landlord determines that Tenant's use of electricity in the
Premises exceeds the electrical demands on a square foot basis of other tenants
in the Building, then Tenant shall pay to Landlord (or the utility company if
direct service is provided by such company) promptly upon demand therefore, for
all such excessive electric consumption and demand. Tenant also shall pay a
service charge related thereto as calculated by Landlord.


                                  PART 7 - USE

          The Premises shall be used solely for general office purposes that are
permitted by applicable zoning ordinances and land use requirements and for no
other purpose. Tenant agrees to use and maintain the Premises in a clean,
careful, safe, lawful, and proper manner.


             PART 8 - COMPLIANCE WITH LAWS AND BUILDING REGULATIONS

          SECTION 8.01.  COMPLIANCE WITH LAWS.

          Tenant shall, at its sole expense, promptly and faithfully (i) comply
with all present and future laws, ordinances, orders, rules, regulations, and
requirements of every governmental authority having jurisdiction over the
Premises; (ii) comply with the provisions of the Americans with Disabilities Act
42 U.S.C. Section 12101 ET SEQ as it applies to the Premises and Tenant's
activities therein; (iii) comply with any direction made pursuant to law by any
public officers which requires abatement of any nuisance or imposes upon
Landlord or Tenant any duty or obligation arising from Tenant's occupancy or use
of the Premises or from conditions which have been created by or at the
insistence of Tenant; (iv) comply with the requirements of the local board of
fire underwriters, or anybody exercising similar functions with respect to the
construction, care and safety, maintenance and operation of the Premises; and
(v) indemnify Landlord and hold Landlord harmless from any loss, cost, claim, or
expense which Landlord may incur or suffer by reason of Tenant's failure to
comply with its obligations under clauses (i), (ii), (iii) or (iv) above. If
Tenant receives notice of any such direction or of violation of any such law,
order, ordinance, or regulation, Tenant shall promptly notify Landlord thereof.


          SECTION 8.02.  OBSERVANCE OF BUILDING'S RULES AND REGULATIONS.

          Tenant and its servants, employees, agents, visitors, and licensees
shall observe faithfully and comply strictly with the Rules and Regulations
attached to this Lease as EXHIBIT "D". Landlord shall at all times have the
right to make reasonable changes in and additions to such Rules and Regulations;
provided such changes in existing or new rules and regulations do not materially
interfere with the lawful conduct of Tenant's business in the Premises. Any
failure by Landlord to enforce any of the Rules and Regulations now or hereafter
in effect, either against Tenant or any other tenant in the Building, shall not
constitute a waiver of any such Rules and Regulations. Except as may be required
by the provisions of Part 20 of this Lease, Landlord shall not be liable to
Tenant for the failure or refusal by any other tenant, guest, invitee, visitor,
or occupant of the Building to comply with any of the Rules and Regulations. If
there is any inconsistency between this Lease and the Rules and Regulations set
forth in EXHIBIT "D" hereto, this Lease shall govern.


          SECTION 8.03.  HAZARDOUS MATERIALS.

          (a) Except for those materials that are necessary in the normal course
of Tenant's business activities associated with the Permitted Use, Tenant, its
agents, employees, contractors or invites shall not (i) cause or permit any
Hazardous Materials (hereinafter defined) to be brought upon, stored, used or
disposed on, in or about the Premises and/or the Building, or (ii) permit the


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release, discharge, spill or emission of any substance considered to be a
Hazardous Material from the Premises.

          (b) Any Hazardous Materials permitted by SUBPARAGRAPH (A), all
containers therefor, and all materials that have been contaminated by Hazardous
Materials shall be used, kept, stored and disposed of by Tenant in a manner that
shall in all respects comply with all applicable federal, state and local laws,
ordinances, regulations and standards.

          (c) Tenant hereby agrees that it is and shall be fully responsible for
all costs, expenses, damages or liabilities (including, but not limited to those
incurred by Landlord and/or its mortgagee) which may occur from the use,
storage, disposal, release, spill, discharge or emissions of Hazardous Materials
by Tenant whether or not the same may be permitted by this Lease. Tenant shall
defend, indemnify and hold harmless Landlord, its mortgagee and its agents from
and against any claims, demands, administrative orders, judicial orders,
penalties, fines, liabilities, settlements, damages, costs or expenses
(including, without limitation, reasonable attorney and consultant fees, court
costs and litigation expenses) of whatever kind or nature, known or unknown,
contingent or otherwise, arising out of or in any way related to the use,
storage, disposal, release, discharge, spill or emission of any Hazardous
Material by Tenant, its agents, employees, contractors or invites. The
provisions of this Section shall be in addition to any other obligations and
liabilities Tenant may have to Landlord at law or in equity and shall survive
the transactions contemplated herein or any termination of this Lease.

          (d) As used in this Lease, the term "HAZARDOUS MATERIALS" shall
include, without limitation:

                   (i) Those substances included within the definitions of
"hazardous substances", "hazardous materials," toxic substances," or "solid
waste" in the Comprehensive Environmental Response Compensation and Liability
Act of 1980 (42 U.S.C. ss.9601 eT Seq.) ("CERCLA"), as amended by Superfund
Amendments and Reauthorization Act of 1986 ("SARA"), the Resource Conservation
and Recovery Act of 1976 ("RCRA"), and the Hazardous Materials Transportation
Act, and in the regulations promulgated pursuant to said laws, all as amended;

                   (ii) Those substances listed in the United States Department
of Transportation Table (49 CFR 172.101 and amendments thereto) or by the
Environmental Protection Agency (of any successor agency) as hazardous
substances (40 CFR Part 302 and amendments thereto);

                   (iii) Any material, waste or substance which is
(A) petroleum, (B) asbestos, (C) polychlorinated biphenyls, (D) designated as a
"hazardous substance" pursuant to Section 311 of the Clean Water Act, 33 U.S.C.
ss.1251 eT Seq. (33 U.S.C. ss.1321) or listed pursuant to Section of the Clean
Water Act (33 U.S.C. ss.1317); (E) flammable explosives; or (F) radioactive
materials;

                   (iv) Those substances regulated pursuant to or identified in
the Virginia Pesticide Law; Air Pollution Control Board; Virginia Waste
Management Act; Environmental Health Service; Transportation of Hazardous
Radioactive Materials; Virginia Hazardous Materials Emergency Response Program;
State Water Control Law; The Groundwater Act of 1973; and Miscellaneous
Offenses; and in the regulations promulgated pursuant to said laws, all as
amended; and

                   (v) Such other substances, materials and wastes which are or
become regulated as hazardous or toxic under applicable local, state or federal
law, or the United States government, or which are classified as hazardous or
toxic under federal, state, or local laws or regulations.


                              PART 9 - ALTERATIONS

          SECTION 9.01.  APPROVAL OF LANDLORD.

          Tenant shall not, at any time during the Term, without Landlord's
prior written consent, make any alterations (structural or otherwise) to the
Premises. Should Tenant desire any


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alterations, Tenant agrees to submit all plans and specifications for same,
including complete architectural plans, to Landlord for Landlord's written
approval, before beginning such work and Landlord's approval shall not be
unreasonably withheld, conditioned or delayed. Landlord shall not be considered
as unreasonably withholding its approval by refusing to consent to any
alterations which would (i) alter the exterior appearance of the Building, or
the public lobbies, corridors, or common areas thereof; (ii) causes or are
likely to cause any weakening of any part of the structure of the Premises or
Building or which may cause damage or disruption to any Building system; or
(iii) violate any underlying ground lease or deed of trust or mortgage. Upon
Tenant's receipt of Landlord's written approval, Tenant may proceed with the
construction of the approved alterations, but only so long as they are in
substantial compliance with the plans and specifications and provisions of this
PART 9. Additionally, the construction of any alterations, the alterations
themselves, or any maintenance thereof shall comply with all building, safety,
fire, plumbing, electrical and other codes, governmental requirements (including
but not limited to Title III of the Americans with Disabilities Act of 1990, all
regulations issued thereunder and the Accessibility Guidelines for Buildings and
Facilities issued pursuant thereto, as the same are in effect on the date hereof
and may be hereafter modified, amended or supplemented) and insurance
requirements, and shall not require an amount of water, electricity, gas, heat,
ventilation, or air-conditioning which exceeds Building Standard unless prior
written arrangements satisfactory to Landlord are made with respect thereto. All
alterations shall be made at Tenant's expense, either by Tenant's contractors
which have been approved in advance by Landlord or, at Landlord's option, by
Landlord's contractors on terms reasonably satisfactory to Tenant. If Landlord's
contractor is performing the alterations, Tenant shall pay to Landlord a fee
equal to five percent (5%) of the actual costs of such work, such fee to cover
Landlord's overhead related to the work, including, but not limited to,
Landlord's review of the plans and specifications, coordination of the work,
consultation with professionals regarding the work, and general administration
allocable to the work; provided that, if Landlord is performing the alterations,
the fee that Tenant shall pay to Landlord shall increase to ten percent (10%) of
the actual costs of such work. Any extraordinary third party costs incurred by
Landlord as a result of Tenant's Alterations work shall be paid by Tenant. All
such construction shall be completed promptly and in a good and workmanlike
manner and shall be performed in compliance with PART 10 hereof.


          SECTION 9.02.  OWNERSHIP OF IMPROVEMENTS TO PREMISES.

          All Leasehold Improvements constructed by Landlord pursuant to EXHIBIT
"B" are and shall remain the property of Landlord, and shall not be removed from
the Premises. At the time of Landlord's approval of Alterations to the Premises,
Landlord shall notify Tenant as to whether the Alterations will be and remain
the Landlord's property, and shall not be removed from the Premises. If Landlord
notifies Tenant that Landlord will not retain the ownership of such Alterations
Tenant shall, at Tenant's sole expense, cause the same to be removed and restore
the Premises to the condition in which they existed prior to the alterations.
Tenant further agrees to remove, at Tenant's expense, all of its furniture,
furnishings, personal property and movable trade fixtures by the Expiration
Date, and to promptly reimburse Landlord for the cost of repairing all damage
done to the Premises or the Building by such removal.


                                 PART 10 - LIENS

          Tenant shall keep the Premises and the Buildings free from any liens
arising from any work performed, materials furnished, or obligations incurred by
or at the request of Tenant, its agents, employees or independent contractors.
If any lien is filed against the Premises, the Building or Tenant's leasehold
interest therein, which arises out of any purported act or agreement of Tenant,
Tenant shall discharge same within thirty (30) days after its filing. If Tenant
fails to discharge such lien within such period, then, in addition to any other
right or remedy Landlord may, at its election, discharge the lien by depositing
with a court or a title company, or by bonding, the amount claimed to be due.
Tenant shall pay on demand, as Additional Rent, any amount paid by Landlord for
the discharge or satisfaction of any such lien, and all attorney's fees and
other costs and expenses of Landlord reasonably incurred in defending any such
action or in obtaining the discharge of such lien, together with all necessary
disbursements in connection therewith.


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                                PART 11 - REPAIRS

          SECTION 11.01.  TENANT'S OBLIGATIONS.

          Except as set forth in PART 5 and SECTION 11.02 of this Lease, Tenant
shall keep the Premises and every part thereof in good condition and repair at
all times during the Term and at Tenant's sole cost and expense. At the end of
the Term, Tenant shall surrender to Landlord the Premises and all alterations,
additions, and improvements thereto in the same condition as when received,
subject to the provisions of PART 17 hereof. Landlord shall give Tenant five (5)
days notice to commence to make repairs, and if Tenant fails to commence to make
such repairs within such time period, Landlord, at its option, may make such
repairs, and Tenant shall pay Landlord, on demand, Landlord's actual costs in
making such repairs plus a fee of ten percent (10%) to cover Landlord's
overhead, all to constitute Additional Rent. Landlord has no obligation and has
made no promise to alter, remodel, improve, repair, decorate, or paint the
Premises or any part thereof, except as specifically set forth in this Lease.


          SECTION 11.02.  LANDLORD'S OBLIGATIONS.

          Subject to the other provisions of this Lease imposing obligations in
this respect upon Tenant, and subject to the provisions of PARTS 13 AND 14
hereof, Landlord shall repair, replace, and maintain (a) the external and
structural parts of the Building and the Building systems and (b) all common
areas.


                               PART 12 - INSURANCE

          SECTION 12.01.  TENANT'S INSURANCE.

          Tenant, at its sole expense, shall obtain and keep in force the
following insurance:

                   (a) Commercial general liability insurance coverage on an
"occurrence basis" against claims for personal injury, including, without
limitation, bodily injury, death, and broad form property damage, in limits not
less than $1,000,000 per occurrence and a $2,000,000 aggregate, with coverage to
include a per location endorsement, contractual liability, fire legal liability
in the amount of $500,000, and other broad form endorsements that would be
carried by a prudent individual conducting a business similar to Tenant's
business. All such insurance policies shall name Tenant as the named insured
thereunder and shall name Landlord and Landlord's mortgagees as additional
insureds thereunder, all as their respective interests may appear;

                   (b) Worker's Compensation and Employer's Liability insurance,
with a waiver of subrogation endorsement waiving rights of subrogation against
Landlord, in form and amount satisfactory to Landlord and at a minimum is equal
to that required by the law of Virginia;

                   (c) Special Causes of Loss Insurance insuring any Leasehold
Improvements made to the Premises after the Commencement Date and Tenant's
interest in the Premises and all property located in the Premises, including
furniture, equipment fittings, installations, fixtures, supplies and any other
personal property, Leasehold Improvements and alterations ("TENANT'S PROPERTY"),
in an amount equal to the full replacement value, it being understood that no
lack or inadequacy of insurance by Tenant shall in any event make Landlord
subject to any claim by virtue of any theft or loss or damage to any uninsured
or inadequately insured property;

                   (d) During the course of construction of any work performed
by Tenant or on Tenant's behalf pursuant to this Lease or any alterations by
Tenant until completion thereof, Builder's Risk Insurance on a "special causes
of loss" basis (including collapse) on a completed value (non-reporting) form
for full replacement value covering all work incorporated in the Building and
all materials and equipment in or about the Premises;


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                   (e) Auto liability coverage for owned, hired and non-owned
vehicles with a $1,000,000 combined single limit; and

                   (f) Excess liability coverage in the amount of $5,000,000
which will follow form and respond to and increase the limits of the coverages
described in SECTIONS 12.01(a), (b), (c), AND (d) above.

          All policies shall be issued by companies having a Best's rating of at
least A-XI and shall be in amounts and in form satisfactory from time to time to
Landlord and Landlord's lender. All policies shall contain an endorsement or
agreement by the insurer that any loss shall be payable in accordance with the
terms of such policy notwithstanding any act or negligence of Tenant which might
otherwise result in a forfeiture of said insurance, and the further agreement of
the insurer waiving all rights of setoff, counterclaim, or deduction against
Tenant. Tenant will deliver certificates of insurance evidencing each policy to
Landlord as soon as practicable after the placing of the required insurance, but
not later than ten (10) days prior to the date Tenant takes possession of all or
any part of the Premises. All policies shall contain an undertaking by their
insurers to notify Landlord and Landlord's lender in writing, by registered or
certified U.S. Mail, return receipt requested, not less than thirty (30) days
before any material change, reduction in the scope or limits of coverage,
cancellation, or other termination thereof. All policies shall name Landlord and
Landlord's manager as additional insureds and shall be evidenced as such on a
Certificate of Insurance issued to Landlord.

          Landlord reserves the right to periodically review the insurance
coverages required by this SECTION 12.01 and to revise such requirements to
reflect insurance industry practices or require other forms or amounts of
insurance as may be reasonably required to reflect changes in insurance industry
practices.


          SECTION 12.02.  INSURANCE RATING.

          Tenant will not keep, use, sell or offer for sale in, or upon the
Premises any article which may be prohibited by any insurance policy
periodically in force covering the Building and the Leasehold Improvements. If
Tenant's occupancy or business in or on the Premises, whether or not Landlord
has consented to the same, results in any increase in premiums for the insurance
periodically carried by Landlord with respect to the Building or the Leasehold
Improvements, Tenant shall pay any such increase in premiums as Additional Rent
within ten (10) days after being billed therefor by Landlord.

          If any of the Landlord's insurance policies shall be canceled or
cancellation shall be threatened or the coverage thereunder reduced or
threatened to be reduced in any way because of the use of the Premises or any
part thereof by Tenant or any assignee or subtenant of Tenant or by anyone
Tenant permits on the Premises and, if Tenant fails to remedy the condition
giving rise to such cancellation, threatened cancellation, reduction of
coverage, or threatened reduction of coverage within forty-eight (48) hours
after written notice thereof, Landlord may, at its option, either terminate this
Lease or enter upon the Premises and attempt to remedy such condition, and
Tenant shall promptly pay the cost thereof to Landlord as Additional Rent.
Landlord shall not be liable for any damage or injury caused to any property of
Tenant or of others located on the Premises resulting from such entry. If
Landlord is unable or elects not to remedy such condition, then Landlord shall
have all of the remedies provided for in this Lease in the event of a Default by
Tenant. Notwithstanding the foregoing provisions of this Section, if Tenant
fails to remedy as aforesaid, Tenant shall be in Default of its obligations
hereunder and Landlord shall have no obligation to remedy such Default.


          SECTION 12.03.  WAIVER OF SUBROGATION.

          All policies covering real or personal property which Tenant obtains
affecting the Premises shall include, if possible, a clause or endorsement
denying the insurer any rights of subrogation


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against Landlord to the extent rights have been waived by the insured before the
occurrence of injury or loss, if same are obtainable. Tenant waives any rights
of recovery against Landlord for injury or loss due to hazards covered by
policies of insurance containing such a waiver of subrogation clause or
endorsement to the extent of the injury or loss covered thereby.


                   PART 13 - DAMAGE BY FIRE OR OTHER CASUALTY

          SECTION 13.01.  DAMAGE TO PREMISES.

          Tenant shall immediately notify Landlord of any damage to the Building
which affects the Premises. If all or any portion of the Premises are damaged or
destroyed by any casualty against which Tenant is required to be insured under
Section 12.01 of the General Lease Provisions, and if, in Landlord's reasonable
opinion, (i) the Premises cannot be rebuilt or made fit for Tenant's purposes
within two hundred seventy (270) days of the damage or destruction, or (ii) the
proceeds from Tenant's insurance required to be maintained by Tenant pursuant to
PART 12 are insufficient to repair or restore the damage or destruction, then
Landlord (with respect to the events in (i) or (ii) above) or Tenant (with
respect to (i) above only) shall have the right to terminate this Lease by
giving the other, within sixty (60) days after such damage or destruction,
written notice of termination, and thereupon Rent and any other payments for
which Tenant is liable under this Lease shall be apportioned and paid to the
date of such damage, and Tenant shall immediately vacate the Premises; provided,
however, that those provisions of this Lease which are designated to cover
matters of termination and the period thereafter shall survive the termination
hereof. Notwithstanding the foregoing, in no event shall Tenant have the right
to terminate this Lease if the damage or destruction of the Premises is a result
of (i) a default by Tenant or (ii) the negligence or willful act of Tenant, or
Tenant's agents, employees, representatives, contractors, successors or assigns,
licensees or invitees.


          SECTION 13.02.  DAMAGE TO BUILDING.

          If the Building or any portion thereof is damaged or destroyed by any
cause whatsoever, to the extent that, (a) in Landlord's reasonable judgment, it
would not be economically feasible to repair or restore such damage or
destruction, or (b) in Landlord's reasonable judgment, the damage or destruction
to the Building cannot be repaired or restored within three hundred sixty (360)
days after such damage or destruction, either Landlord or Tenant may, at their
option, terminate this Lease by giving notice of such termination to the other
party within sixty (60) days after such damage or destruction.


          SECTION 13.03.  PARTIAL DAMAGE.

          In the event of partial destruction or damage to the Building or the
Premises which is not subject to SECTION 13.01 OR 13.02, but which renders the
Premises partially, but not wholly untenantable, this Lease shall terminate as
to the portion of the Premises which, in Landlord's reasonable opinion, cannot
be used or occupied by Tenant as a result of such casualty and shall remain in
effect as the remainder of the Premises. Landlord shall in such event, within a
reasonable time after the date of such destruction or damage, subject to Tenant
Delay and to the extent and availability of insurance proceeds, restore the
Premises to as near the same condition as existed prior to such partial damage
or destruction, provided that Tenant pays to Landlord Tenant's insurance
proceeds as required in SECTION 13.05 of the General Lease Provisions. In no
event shall Rent abate or shall any termination occur if damage to or
destruction of the Premises is the result of either (i) a default by Tenant or
(ii) the negligence or willful act of Tenant, or Tenant's agents, employees,
representatives, contractors, successors or assigns, licensees or invitees.


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          SECTION 13.04.  DAMAGE DURING LAST YEAR OF TERM.

          If the Building or the Premises or any portion thereof is destroyed by
fire or other causes at any time during the last year of the Term, then either
Landlord or Tenant shall have the right, at the option of either party, to
terminate this Lease by giving written notice to the other within sixty (60)
days after the date of such destruction.


          SECTION 13.05.  NO LANDLORD LIABILITY.

          Landlord shall have no liability to Tenant for inconvenience, loss of
business, or annoyance arising from any repair of any portion of the Premises or
the Building. If Landlord is required by this Lease or by any lender or lessor
of Landlord to repair or if Landlord undertakes to repair, Tenant shall pay to
Landlord that amount of Tenant's insurance proceeds which insures such damage as
a contribution towards such repair, and Landlord shall use reasonable efforts to
have such repairs made promptly and in a manner which will not unnecessarily
interfere with Tenant's occupancy.


          SECTION 13.06.  APPORTIONMENT OF RENT.

          In the event of termination of this Lease pursuant to this PART 13,
then all Rent shall be apportioned and paid to the date on which possession is
relinquished or the date of such damage, whichever last occurs, and Tenant shall
immediately vacate the Premises according to such notice of termination;
provided, however, that those provisions of this Lease which are designated to
cover matters of termination and the period thereafter shall survive the
termination hereof.


                             PART 14 - CONDEMNATION

          SECTION 14.01.  ENTIRE BUILDING.

          In the event that the whole or substantially the whole of the Building
and/or the Premises are taken or condemned for any public purposes, this Lease
and the leasehold estate created hereby shall cease and terminate as of the date
of such taking.


          SECTION 14.02.  PORTION OF BUILDING.

          In the event that any portion of the Building shall be taken or
condemned for any public purpose (whether or not such taking includes any
portion of the Premises), which taking, in Landlord's sole judgment, shall
interfere materially with Landlord's use and operation of the Building or is
such that Landlord determines that the Building cannot be restored to usefulness
in an economically feasible manner, then Landlord shall have the option to
terminate this Lease, effective as of the date specified by Landlord in its
notice of termination.


          SECTION 14.03.  PORTION OF PREMISES.

          In the event that a portion, but less than substantially the whole, of
the Premises should be taken or condemned for any public purpose, then this
Lease shall be terminated as of the date of such taking as to the portion of the
Premises so taken, and, unless Landlord exercises its option to terminate this
Lease pursuant to SECTION 14.02 above, this Lease shall remain in full force and
effect as to the remainder of the Premises. In such event, the Rent will be
diminished by an amount representing the part of such amounts properly
applicable to the portion of the Premises so taken. Further, in such event
Tenant's Proportionate Share shall be recomputed based upon the remaining
Rentable Area in the Premises and in the Building.


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          SECTION 14.04.  TERMINATION OF LEASE.

          In the event of the termination or partial termination of this Lease
pursuant to the provisions of this Part 14, this Lease and the Term and the
estate hereby granted shall expire as of the date of such termination in the
same manner and with the same effect as if that were the date set for the normal
expiration of the Term of this Lease, and the Rent shall be apportioned as of
such date.


          SECTION 14.05.  LANDLORD'S RIGHT TO AWARD.

          All awards, damages, and other compensation paid by the condemning
authority on account of such taking or condemnation (or sale under threat of
such a taking) shall belong to Landlord, and Tenant hereby assigns to Landlord
all rights to such awards, damages and compensation. Tenant agrees not to make
any claim against Landlord or the condemning authority for any portion of such
award or compensation attributable to damages to the Premises, the value of the
unexpired term of this Lease, the loss of profits or goodwill, leasehold
improvements, or severance damages. Nothing contained herein, however, shall
prevent Tenant from pursuing a separate claim against the condemning authority
for the value of Non-Building Standard Leasehold Improvements paid entirely by
the Tenant, furnishings, equipment, and trade fixtures installed in the Premises
at Tenant's expense and for relocation expenses, provided that such claim does
not in any way diminish the award or compensation payable to or recoverable by
Landlord in connection with such taking or condemnation.


                       PART 15 - ASSIGNMENT AND SUBLETTING

          SECTION 15.01.  RIGHTS OF TENANT.

          (a) Tenant may not sell, assign, transfer, or hypothecate this Lease
or any interest herein (either voluntarily or by operation of law, and
including, if Tenant is a corporation, partnership or limited liability company,
the sale or transfer of a controlling interest in Tenant), or sublet the
Premises or any part thereof without the prior written consent of Landlord. If
Tenant should desire to assign this Lease or sublet the Premises (or any part
thereof) and provided that Tenant is not then in default hereunder, Tenant shall
give Landlord written notice at least thirty (30) days in advance of the date on
which Tenant desires to make such assignment or sublease. Landlord shall then
have a period of fifteen (15) days following receipt of such notice within which
to notify Tenant in writing that Landlord elects:

                   (1) if Tenant desires to assign or sublease certain space for
the remainder of the Term, to terminate this Lease as to the space so affected
as of the date specified by Tenant in its notice, in which event Tenant, subject
to the provisions of this Lease which expressly survive the termination hereof,
shall be relieved of all further obligations hereunder as to such space; or

                   (2) to permit Tenant to assign or sublet such space, subject,
however, to the subsequent written approval by Landlord of the instrument of
assignment or sublease as to form and substance and of the proposed assignee or
subtenant; or

                   (3) to refuse, in Landlord's sole discretion, to consent to
Tenant's assignment or subleasing of such space and to continue this Lease in
full force and effect as to the entire Premises. If Landlord should fail to
notify Tenant in writing of such election within such fifteen (15) day period,
Landlord shall be deemed to have elected option (2) above.

          (b) Except as may be otherwise expressly set forth to the contrary, no
assignment or subletting by Tenant shall relieve Tenant of Tenant's obligations
under this Lease. Any attempted assignment or sublease by Tenant in violation of
the terms and provisions of this SECTION 15.01 shall be void.

          (c) For the purposes of this SECTION  15.01, the following shall be
deemed an assignment of this Lease.


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                   (1) If Tenant is a corporation, the stock of which is not
listed on a "national securities exchange" (as defined in the Securities Act of
1934), then the sale, issuance or transfer (whether cumulatively or in a single
transaction), of stock by Tenant or the shareholders of record, as of the date
hereof, the result of which either changes or makes possible the change in the
voting control of Tenant; and

                   (2) If Tenant is a joint venture, partnership, limited
liability company or other association (collectively referred to as the
"PARTNERSHIP"), the sale, issuance or transfer (whether cumulatively or in a
single transaction) of ownership of the entity the result of which changes the
management of the entity or the voting control of the entity.

          (d) Landlord's consent to an assignment or sublease shall not be
unreasonably withheld, conditioned or delayed, provided all of the following
conditions have been satisfied:

                   (1) if a sublease, the sublease must have provisions which
satisfy subparagraph (e) hereof;

                   (2) the entity, organization, or individual to which such
space is proposed to be sublet is of a type similar to the existing tenants in
Fair Lakes, is not of a type that would be an undesirable tenant in a
first-class office complex in Fair Lakes, or is not of a type that because of
its controversial or unsavory nature, might bring undue notoriety or disruption
to the Building;

                   (3) if an assignment, the entity to which Tenant desires to
assign has financial credit that is equal to or greater than that of Tenant on
the Effective Date in Landlord's sole discretion;

                   (4) the entity to which Tenant desires to sublease is not
then a tenant in the Building and is not then in negotiations with Landlord for
the lease of space in the Building; and

                   (5) the assignment or sublease will not violate any exclusive
or restriction in any other lease of space in Fair Lakes by Landlord or its
Affiliates (as defined in SECTION 15.04).

          (e) A sublease of portions of the Premises, must include (or shall be
deemed to include) provisions stating that it is subject and subordinate to this
Lease and to the matters to which this Lease is or shall be subordinate, and
that in the event of the termination of this Lease, or the re-entry or
dispossession of Tenant by Landlord under this Lease, Landlord, at its option,
may either terminate the sublease, in which case the subtenant shall peacefully
vacate the premises sublet, or, require the subtenant to attorn to Landlord as
its sublessor pursuant to the then applicable terms of such sublease for the
remaining term thereof, except that Landlord shall not be (i) liable for any
previous act or omission of Tenant as sublessor under such sublease, (ii)
subject to any offset which theretofore accrued to such subtenant against
Tenant, or (iii) bound by any previous modification of such sublease not
consented to in writing by Landlord or by a previous prepayment of rent more
than one month in advance. A sublease also must provide that all Rent payments
to be made by the subtenant must be made through Tenant and not directly by
subtenant to Landlord.


          SECTION 15.02.  EXCESS RENT.

          If the rent agreed upon between Tenant and its proposed subtenant
under any proposed sublease of the Premises (or any part hereof) is greater than
the Base Rent, that Tenant must pay Landlord hereunder for that portion of the
Premises that is subject to such proposed sublease, then fifty percent (50%) of
such excess rent (after deducting therefrom reasonable costs for brokerage
commissions, construction expenses for tenant improvements and legal and
advertising fees) shall be considered Additional Rent owed by Tenant to
Landlord, and shall be paid by Tenant to Landlord in the same manner that Tenant
pays rent under this Lease.


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          SECTION 15.03.  RIGHTS OF LANDLORD.

          Landlord may sell, transfer, assign, and convey, all or any part of
the Building and/or the Land and any and all of its rights under this Lease, and
in the event Landlord assigns its rights under this Lease and provides written
notice of such assignment to Tenant, Landlord shall be released from any further
obligations hereunder, and Tenant agrees to look solely to Landlord's successor
in interest for performance of such obligations.


          SECTION 15.04.    AFFILIATE TRANSFER.

          Notwithstanding the provisions of SECTION 15.01 hereof, Tenant shall
have the right, without the prior written consent of Landlord, to assign its
entire interest in this Lease to an Affiliate (hereinafter defined) so long as
(i) the Affiliate deliver to Landlord, concurrently with such assignment, a
written notice of the assignment and an assumption agreement whereby the
Affiliate assumes and agrees to perform, observe and abide by the terms,
conditions, obligations and provisions of this Lease applicable to Tenant, (ii)
the Affiliate has financial credit that is equal to or greater than that of
Tenant on the Effective Date, and (iii) the entity remains an Affiliate.
Further, Tenant shall also have the right, without the prior written consent to
Landlord, to sublet all or any portion of the Premises to an Affiliate so long
as (i) such sublease satisfies the requirements of this Section, (ii) the
Affiliate has financial credit that is equal to or greater than that of Tenant
on the Effective Date, and (iii) the entity remains an Affiliate. No subletting
or assignment by Tenant made pursuant to this Section shall relieve Tenant of
Tenant's obligations under this Lease. As used herein, the term Affiliate shall
mean and collectively refer to (i) a corporation, individual or other entity
which owns and controls all of the voting stock of Tenant (if it is a
corporation) or controls the day-to-day decision making of Tenant (the
"Parent"), or (ii) a corporation in which either the Tenant or its Parent owns
and controls all of the voting stock of the corporation and is able to elect (by
ownership of stock or proxy) the board of directors and the officers of the
corporation, or (iii) an Affiliate of the Parent, and/or (iv) a successor or
surviving corporation in the event of a merger, takeover or other form of
corporate acquisition of the Tenant. A transfer permitted under this Section
will be excluded from the provisions of SECTION 15.02 hereof.


                            PART 16 - INDEMNIFICATION

          Tenant waives all claims against Landlord for damage to any property
or injury to, or death of, any person, in, upon, or about the Building or the
Premises, arising at any time and from any cause except to the extent such
damage is caused by reason of the negligence or willful misconduct of Landlord,
its agents, employees, representatives, or contractors, and Tenant shall
indemnify Landlord and shall hold Landlord harmless from any damage to any
property or injury to, or death of, any person arising from the use of the
Building or the Premises by Tenant or its agents, employees, representatives,
contractors, or invitees, except to the extent such damage, injury or death is
caused by the negligence or willful misconduct of Landlord, its agents,
employees, representatives, or contractors. Tenant's foregoing indemnity
obligation shall include reasonable attorney's fees and all other costs and
expenses reasonably incurred by Landlord from the first notice that any claim or
demand has been made or may be made.

          The provisions of this PART 16 shall survive the termination of this
Lease for any reason with respect to any damage, injury, or death occurring
before such termination.

          If Landlord is made a party to any litigation commenced by or against
Tenant or relating to this Lease or to the Premises, and provided that in any
such litigation Landlord is not finally adjudicated to be at fault, then Tenant
shall pay all costs and expenses to the extent such costs and expenses are not
attributable to Landlord's fault, including reasonable attorneys' fees and court
costs, incurred by or imposed upon Landlord because of any such litigation, and
the amount of such costs and expenses, including reasonable attorneys' fees and
court costs, shall be a demand obligation owing by Tenant to Landlord and shall
constitute Additional Rent.


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<PAGE>
                       PART 17 - SURRENDER OF THE PREMISES

          SECTION 17.01.  CONDITION OF PREMISES.

          Upon expiration of the Term or other termination of this Lease for any
cause whatsoever, Tenant shall peacefully vacate the Premises in as good order
and condition as the same were at the beginning of the Term or may thereafter
have been improved by Landlord or Tenant, except for reasonable use and wear
thereof and damage to the Premises by fire or other casualty or condemnation.


          SECTION 17.02.  TENANT HOLDOVER.

          In the event that Tenant shall not immediately surrender the Premises
on the Expiration Date of the Term, Tenant, at the option of Landlord, shall
become a month-to-month Tenant at one hundred fifty percent (150%) of the Rent
in effect during the last month of the Term and subject to all of the terms,
conditions, covenants and agreements of this Lease; provided, however, that if
Landlord has executed a lease for space in the Building, then Tenant shall be
obligated to pay Landlord twice the Rent in effect during the last month of the
Term. Tenant shall give to Landlord at least thirty (30) days' written notice of
any intention to quit the Premises, and Tenant shall be entitled to thirty (30)
days' written notice to quit the Premises, unless Tenant is in Default
hereunder, in which event Tenant shall not be entitled to any notice to quit,
the usual thirty (30) days' written notice to quit being hereby expressly
waived. Notwithstanding the foregoing provisions of this Section, in the event
that Tenant shall hold over after the expiration of the Term, then at any time
prior to Landlord's acceptance of Rent from Tenant as a monthly Tenant
hereunder, Landlord, at its option, may forthwith re-enter and take possession
of the Premises without process, or by any legal process in force in the
Commonwealth of Virginia. Tenant shall be liable to Landlord for all damage
which Landlord suffers because of any holding over by Tenant, and Tenant shall
indemnify Landlord against all claims made against Landlord resulting from
Landlord's delay in delivering possession of the Premises to any other tenant or
prospective tenant.


                         PART 18 - ESTOPPEL CERTIFICATES

          Tenant shall execute and return within ten (10) calendar days any
certificate or agreement that Landlord may request in writing from time to time,
stating that this Lease is unmodified and in full force and effect, or in full
force and effect as modified, and stating the modification. The certificate also
shall state (i) that all work has been completed, and the work and the Premises
are accepted as satisfactory except for items listed on a punch list, if any,
attached to such certificate; (ii) the amount of Base Rent and Additional Rent
and the dates on which Rent commenced to accrue and to which the Rent has been
paid in advance, and the amount of any security deposit or prepaid Rent; (iii)
that Tenant is paying Rent on a current basis; (iv) that Tenant is in full and
complete possession of the Premises and doing business; (v) that there is no
present default on the part of Landlord, or attach a memorandum stating any such
instance of default; (vi) that Tenant has not advanced any amounts to or on
behalf of Landlord which have not been reimbursed; (vii) that Tenant has no
rights to setoff and no defense or counterclaim against enforcement of its
obligations under the Lease, including the payment of Rent; (viii) that Tenant
understands that this Lease has been collaterally assigned to Landlord's
mortgagee as security for a loan to Landlord and that Rent may not be prepaid
other than as may be provided for in this Lease nor may this Lease be amended,
modified, or waived so as to have a material impact on the financial obligations
of either Tenant or Landlord without such mortgagee's prior written approval;
(ix) that there are no actions, whether voluntary or otherwise, pending against
Tenant under the bankruptcy laws of the United States or any state thereof; (x)
that Tenant has no other notice of any sale, transfer or assignment of this
Lease or of the Rent; and (xi) any other fact pertaining to Tenant's interest in
this Lease which Landlord, or Landlord's mortgagee, may request. Failure to
deliver the certificate within ten (10) calendar days shall be conclusive upon
Tenant for the benefit of Landlord and any successor to Landlord that this Lease
is in full force and effect and has not been modified except as may be
represented by the party requesting the certificate. Any such certificate may be
relied upon by any


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prospective purchaser, any ground lessor, or any beneficiary under the deed of
trust on the Building, the underlying land, or any part thereof.


                     PART 19 - SUBORDINATION AND ATTORNMENT

         SECTION 19.01.  EXISTING FINANCINGS.

          (a) This Lease is subject and subordinate to any deeds of trust or
other security instruments which, as of the date of this Lease, cover the
Building, the underlying land, or any interest of Landlord therein, and to any
advances made on the security thereof, and to any increases, renewals,
modifications, consolidations, and extensions of any of such deeds of trust or
security instruments (the "EXISTING INDEBTEDNESS"). Landlord agrees to provide
notice to Tenant of such deeds of trust or other security instruments covering
the Building. This provision is declared by Landlord and Tenant to be
self-operative and no further instrument shall be required to effect such
subordination of this Lease. Upon demand, however, Tenant shall execute,
acknowledge, and deliver to Landlord any further instruments and certificates
evidencing such subordination as Landlord, or the holder of the Existing
Indebtedness may reasonably require.

          (b) Landlord agrees to obtain from the holder of the Existing
Indebtedness a Subordination, Non-Disturbance and Attornment Agreement, in form
similar to that attached hereto as EXHIBIT "F" (and by this reference
incorporated herein), which provides that, in the event of a foreclosure or a
transfer in lieu thereof, Tenant will not be disturbed in its possession and
this Lease shall, notwithstanding the foreclosure or transfer in lieu thereof,
continue in full force and effect upon and subject to all terms, covenants,
conditions, and obligations of this Lease so long as (i) no Default has occurred
on the part of Tenant under this Lease and (ii) Tenant attorns to the purchaser
or transferee as landlord under this Lease. Landlord agrees to use good faith
efforts to obtain revisions reasonably requested by Tenant to the Subordination,
Non-Disturbance and Attornment Agreement from the lender of the Existing
Indebtedness.


          SECTION 19.02.  FUTURE FINANCINGS.

          During the Term of this Lease, Landlord reserves the right to encumber
its interest in this Lease, the Building and/or the underlying land, by new or
additional deeds of trust or other security instruments and to refinance the
Existing Indebtedness (the "New Financing"). Tenant agrees to subordinate this
Lease to any New Financing so long as the holder of the New Financing executes
and delivers to Tenant a Subordination, Non-Disturbance and Attornment Agreement
which contains the provision set forth in Section 19.01(b) hereof.


          SECTION 19.03.  ATTORNMENT.

          Provided the holder of the Existing Indebtedness and New Financing has
delivered to Tenant a Subordination, Non-Disturbance and Attornment Agreement
which satisfies the provisions of Section 19.01(b) hereof, Tenant shall attorn
to the purchaser upon a sale or to the grantee under any deed in lieu of
foreclosure and shall recognize such purchaser or grantee as Landlord under this
Lease without any change in the terms or other provisions of this Lease. In such
agreement, Tenant will waive the right, if any, to elect to terminate this Lease
or to surrender possession of the Premises in the event of foreclosure of and
deed of trust or security instrument (or any transfer in lieu thereof).


                            PART 20 - QUIET ENJOYMENT

          Provided Tenant performs all of Tenant's obligations under this Lease,
including the payment of Rent, Tenant shall, during the Term, peaceably and
quietly enjoy the Premises without disturbance from Landlord or any other
persons acting by, through, or under Landlord; subject,


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however, to (i) the terms of this Lease; (ii) the deeds of trust, ordinances,
restrictive covenants, leases, easements, and other agreements or encumbrances
now or hereafter affecting the Building or the land on which the Building is
situated; (iii) the right of Landlord to construct on its property any
additional buildings or other improvements now or hereafter permitted by the
governmental authorities having jurisdiction over Landlord's property; and (iv)
the right of Landlord to relocate parking spaces for the Building, conduct
renovations to the Building or make alterations to the Building so long as
Landlord's exercise of these rights does not substantially interfere with
Tenant's use of the Premises. This covenant and all other covenants of Landlord
in this Lease shall be binding upon Landlord and its successors only with
respect to breaches occurring during its and their respective ownership of
Landlord's interest hereunder.


              PART 21 - SIGNS; FURNISHINGS; COMMUNICATION EQUIPMENT

          SECTION 21.01.  SIGNS AND ADVERTISEMENTS.

          No sign, advertisement, or notice referring to Tenant shall be
inscribed, painted, affixed, or otherwise displayed on any part of the exterior
or the interior of the Building, except those installed by Landlord on the
directories and the entrance door to the Premises and such other areas, if any,
as Landlord may determine. As long as Tenant leases all of the Rentable Area in
the Building and occupies for normal business purposes at least fifty percent
(50%) of the Rentable Area in the Building (with such other Rentable Area being
occupied for normal business purposes by Tenant's permitted assignees or
sublessees), then Tenant shall have the exclusive right, at its sole cost and
expense, to (i) install a sign on the top level exterior of the Building and
(ii) install a monument sign at the main drive or parking entrance to the
Building bearing Tenant's then current corporate logo as it uses in its business
(collectively, the "SIGNS"). The Signs shall conform to all applicable zoning
and governmental ordinances and the Fair Lakes signage standards and shall be
subject to the reasonable approval of Landlord and the Fair Lakes League as to
location, size and design. Tenant shall be obligated, at its sole cost and
expense, to install, maintain, repair and remove the Signs. If Tenant exhibits
or installs any sign, advertisement or notice except the Signs, Landlord shall
have the right to remove the same at Tenant's expense. Landlord shall have the
right to prohibit any advertisement of or by Tenant which in its opinion tends
to impair the reputation of the Building or its desirability as a high-quality
office building and, upon written notice from Landlord, Tenant shall immediately
refrain from and discontinue any such advertisement. Except as otherwise set
forth above, Landlord reserves the right to affix, install, and display signs,
advertisements, and notices on any part of the exterior or interior of the
Building.


          SECTION 21.02.  FURNISHINGS.

          Landlord shall have the right to prescribe the weight and position of
safes and other heavy equipment and fixtures, which, if considered necessary by
Landlord, shall be installed in such manner as Landlord directs in order to
distribute their weight adequately. In no event shall Tenant place on any part
of the floor of the Premises a load exceeding the floor load per square foot
which such floor was designed to carry and which is allowed by law. Any and all
damage or injury to the Premises or the Building caused by moving such heavy
equipment or fixtures or the same being in or upon the Premises, shall be
repaired by and at the sole cost of Tenant. All furniture, equipment, and other
bulky matter of any description shall be delivered to the Premises only through
the designated service entrance of the Building and the designated service
elevator during normal business hours or as otherwise directed or scheduled by
Landlord. All moving of furniture, equipment, and other materials shall be under
the supervision of Landlord, who shall not, however, be responsible for any
damage to or charges for moving the same. Tenant agrees to remove promptly from
the sidewalks adjacent to the Building any of Tenant's furniture, equipment, or
other material there delivered or deposited.


          SECTION 21.03.  COMMUNICATIONS EQUIPMENT.


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          Tenant shall have the right, subject to provisions of this SECTION
21.03 and the License Agreement to be executed by Tenant, to install, operate
and maintain, at Tenant's sole cost and expense, land lines between the Building
and the Fair Lakes V or Fair Lakes VI buildings (so long as Tenant is leasing
space in such buildings) antennas and other support structures reasonably
required for the conduct of Tenant's day-to-day business ("COMMUNICATIONS
EQUIPMENT"). The Communications Equipment shall be limited to receive-only
antennas and land lines necessary for the conduct of Tenant's normal business
activities and shall not be used for the purpose of transmitting for commerce or
reselling antenna transmissions services or other services for a profit. Prior
to the installation of any Communications Equipment, Tenant shall execute the
License Agreement which shall include, among other things, requirements that (i)
the plans and specifications for the proposed Communications Equipment conform
with all laws and applicable regulations and are subject to Landlord's prior
approval, and (ii) such Communications Equipment shall not interfere with other
satellite or communications equipment previously installed in Fair Lakes or
typically used for general office uses. Tenant shall pay to Landlord a monthly
fee (the "LICENSE FEE") equal to (i) $300.00 per pole-type antenna or satellite
dish with a diameter smaller than thirty-six inches (36") and (ii) $500.00 per
pole-type antenna or satellite dish with a diameter equal or greater than
thirty-six inches (36"). The License Fee amount shall increase by three percent
(3%) per year commencing on the first (1st) anniversary of the Commencement Date
and on each anniversary thereafter.


                         PART 22 - DEFAULTS AND REMEDIES

          SECTION 22.01.  EVENTS OF DEFAULT.

          The occurrence of any one or more of the following events shall
constitute a Default or an Event of Default under this Lease: (a) if Tenant
fails to pay any Base Rent hereunder as and when such Rent becomes due and such
failure shall continue for more than five (5) days after Landlord gives Tenant
written notice of past due Rent; (b) if Tenant fails to pay Rent on time more
than three (3) times in any period of twelve (12) months, notwithstanding that
such payments have been made within the applicable cure period; (c) if the
Premises become vacant, deserted, or abandoned for more than ninety (90)
consecutive days or if Tenant fails to take possession of the Premises and
commence business operations therein on the Commencement Date or promptly
thereafter; (d) if Tenant permits to be done anything which creates a lien upon
the Premises and fails to discharge, or bond such lien or post such security
with Landlord as is required by Part 10; (e) if Tenant violates the provisions
of PART 15 by attempting to make an unpermitted assignment or sublease; (f) if
Tenant fails to maintain in force all policies of insurance required by this
Lease and any such failure shall continue for more than ten (10) days after
Landlord gives Tenant notice of such failure; (g) if any petition is filed by or
against Tenant under any present or future section or chapter of the Bankruptcy
Code, or under any similar law or statute of the United States or any state
thereof (which, in the case of an involuntary proceeding, is not permanently
discharged, dismissed, stayed, or vacated, as the case may be, within sixty (60)
days of commencement), or if any order for relief shall be entered against
Tenant in any such proceedings; (h) if Tenant becomes insolvent or makes a
transfer in fraud of creditors or makes an assignment for the benefit of
creditors; (i) if a receiver, custodian, or trustee is appointed for the
Premises or for all or substantially all of the assets of Tenant, which
appointment is not vacated within sixty (60) days following the date of such
appointment; (j) if Tenant fails to perform or observe any other term of this
Lease, including without limitation the payment of Additional Rent, and such
failure shall continue for more than ten (10) days after Landlord gives Tenant
written notice of such failure, or, if such failure cannot be corrected within
such ten (10) day period, if Tenant does not commence to correct such default
within said ten (10) day period and thereafter diligently prosecute the
correction of same to completion within a reasonable time and in any event prior
to the time failure to complete such correction could cause Landlord to be
subject to prosecution for violation of any law, rule, ordinance or regulation
or causes, or could cause a default under any deed of trust, mortgage,
underlying lease, tenant lease or other agreement applicable to the Building or
the land upon which it is situated; (k) it Tenant fails to perform any term
(other than the payment of Rent) of this Lease more than three (3) times in any
period of twelve (12) months, notwithstanding that Tenant has corrected any
previous failures within the applicable cure period; or (l) Tenant is in Default
under any lease for space in Fair Lakes VI or Fair Lakes IV.


                                                                            C-23
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

          SECTION 22.02.  REMEDIES.

          Upon the occurrence of any Event of Default, Landlord shall have the
right, at Landlord's option, to terminate this Lease. With or without
terminating this Lease, Landlord may re-enter and take possession of the
Premises and the provisions of this SECTION 22.02 shall operate as a notice to
quit, any other notice to quit or of Landlord's intention to re-enter the
Premises being hereby expressly waived. If necessary, Landlord may proceed to
recover possession of the Premises under and by virtue of the laws of the
Commonwealth of Virginia or by such other proceedings, including re-entry and
possession, as may be applicable. If Landlord elects to terminate this Lease,
everything contained in this Lease on the part of Landlord to be done and
performed shall cease without prejudice; subject, however, to the right of
Landlord to recover from Tenant all Rent and other sums accrued up to the time
of termination or recovery of possession by Landlord, whichever is later.
Whether or not this Lease is terminated by reason of Tenant's Default, Landlord
may, but shall not be obligated to, relet the Premises for such rent and upon
such terms as are not unreasonable under the circumstances and, if the entire
Rent provided in this Lease plus the costs, expenses, and damages hereafter
described shall not be realized by Landlord, Tenant shall be liable for all
damages sustained by Landlord, including, without limitation, deficiencies in
Base Rent, Adjusted Rent and Additional Rent, the value of any rent abatement,
tenant allowance or other payments made to Tenant, attorney's fees and expenses
reasonably incurred, brokerage fees, and the expense of placing the Premises in
first-class rentable condition. Landlord shall in no way be responsible or
liable for any failure to collect any rent due and/or accrued from such
reletting, to the end and intent that Landlord may elect to hold Tenant liable
for the Base Rent, Adjusted Rent, and Additional Rent, and any and all other
items of cost and expense which Tenant shall have been obligated to pay
throughout the remainder of the Term. Any damages or loss of rent sustained by
Landlord may be recovered by Landlord, at Landlord's option, at the time of the
reletting, or in separate actions, from time to time, as said damage shall have
been made more easily ascertainable by successive relettings. The provisions
contained in this SECTION 22.02 shall be in addition to, and shall not prevent
the enforcement of, any claim Landlord may have against Tenant for anticipatory
breach of this Lease.


          SECTION 22.03.  REMEDIES CUMULATIVE.

          All rights and remedies of Landlord set forth herein are in addition
to all other rights and remedies available to Landlord at law or in equity. All
rights and remedies available to Landlord hereunder or at law or in equity are
expressly declared to be cumulative. The exercise by Landlord of any such right
or remedy shall not prevent the concurrent or subsequent exercise of any such
right or remedy. No delay in the enforcement or exercise of any such right or
remedy shall constitute a waiver of any Default by Tenant hereunder or of any of
Landlord's rights or remedies in connection therewith. Landlord shall not be
deemed to have waived any Default by Tenant hereunder unless such waiver is set
forth in a written instrument signed by Landlord. If Landlord waives in writing
any Default by Tenant, such waiver shall not be construed as a waiver of any
covenant, condition, or agreement set forth in this Lease except as to the
specific circumstances described in such written waiver.


          SECTION 22.04.  NO ACCEPTANCE OR SURRENDER.

          No act or thing done by Landlord or its agents during the Term shall
constitute an acceptance of an attempted surrender of the Premises, and no
agreement to accept a surrender of the Premises shall be valid unless made in
writing and signed by Landlord. No re-entry or taking possession of the Premises
by Landlord shall constitute an election by Landlord to terminate this Lease,
unless a written notice of such intention is given to Tenant. Notwithstanding
any such reletting or re-entry or taking possession, Landlord may at any time
thereafter terminate this Lease for a previous Default. Landlord's acceptance of
Rent following an Event of Default hereunder shall not be construed as a waiver
of such Event of Default. No waiver by Landlord of any breach of this Lease
shall constitute a waiver of any other violation or breach of any of the terms
hereof.


                                                                            C-24
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

Forbearance by Landlord to enforce one or more of the remedies herein provided
upon a breach hereof shall not constitute a waiver of any other breach of this
Lease.


          SECTION 22.05.  CUSTOMS AND PRACTICES.

          No custom or practice which may develop between the parties in the
administration of the terms of this Lease shall be construed to waive or lessen
Landlord's right to insist upon strict performance of the terms of this Lease.


          SECTION 22.06.  PAYMENT OF TENANT'S OBLIGATIONS BY LANDLORD.

          In the Event of Default, Landlord may, but shall not be required to,
make such payment or do such act required to be performed by Tenant. If Tenant
fails to act and Landlord makes such payment or does such act, all costs and
expenses incurred by Landlord, plus interest thereon at the Default Rate from
the date paid by Landlord to the date of payment thereof by Tenant, shall be
immediately paid by Tenant to Landlord. The taking of such action by Landlord
shall not be considered as a cure of such Default by Tenant or to prevent
Landlord from pursuing any remedy it is otherwise entitled to in connection with
such Default.


          SECTION 22.07.  DEFAULT BY LANDLORD.

          Tenant agrees to give written notice of any default by Landlord under
this Lease to any lender of Landlord secured by the Premises upon request
thereof by such lender and a reasonable time within which to cure such default
prior to Tenant taking any action to remedy such default or cancel the Lease.


                           PART 23 - SECURITY DEPOSIT

          SECTION 23.01.  APPLICATION OF SECURITY DEPOSIT.

          On or before August 1, 1999, Tenant shall deliver to Landlord half
(1/2) the sum stipulated in the Basic Lease Information as a Security Deposit.
On or before the Commencement Date, Tenant shall deliver to Landlord the balance
of the sum stipulated in the Basic Lease Information as a Security Deposit.
Landlord shall be required to maintain such deposit in a separate account if
such deposit is made in cash. The Security Deposit shall be security for the
performance by Tenant of all of Tenant's obligations, covenants, conditions, and
agreements under this Lease. Within thirty (30) days after the expiration of the
Term, and provided Tenant has vacated the Premises and is not in Default
hereunder, Landlord shall return the Security Deposit to Tenant, less such
portion thereof as Landlord shall have appropriated to satisfy any Default by
Tenant hereunder. In the event of any Default by Tenant hereunder, Landlord
shall have the right, but shall not be obligated to use, apply or retain all or
any portion of the Security Deposit for (i) the payment of any Base Rent,
Additional Rent or any other sum as to which Tenant is in Default, (ii) the
payment of any amount which Landlord may spend or become obligated to spend to
repair physical damage to the Premises or the Building pursuant to PART 11
hereof, or (iii) the payment of any amount Landlord may spend or become
obligated to spend or for compensation of Landlord for any losses incurred by
reason of Tenant's Default, including, but not limited to, any damage or
deficiency arising in connection with the reletting of the Premises. If any
portion of the Security Deposit is so used or applied, within three (3) business
days after written notice to Tenant of such use or application, Tenant shall
deposit with Landlord an amount sufficient to restore the Security Deposit to
its original amount, and Tenant's failure to do so shall constitute a Default
under this Lease.


                                                                            C-25
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

          SECTION 23.02.  TRANSFER OF SECURITY DEPOSIT.

          In the event of the sale or transfer of Landlord's interest in the
Building, Landlord shall transfer the Security Deposit to the purchaser or
assignee, in which event Tenant shall look only to the new landlord for the
return of the Security Deposit (subject to the provisions of this Lease), and
Landlord shall thereupon be released from all liability to Tenant for the return
of the Security Deposit.


          SECTION 23.03.  LETTER OF CREDIT.

          Provided the conditions of this SECTION 23.03 have been satisfied,
Tenant shall have the right to post a letter of credit as the Security Deposit.
The letter of credit shall (i) be issued by a federally insured bank having an
office in the Washington, D.C. metropolitan area which is reasonably acceptable
to Landlord; (ii) be irrevocable; (iii) authorize the Landlord to draw by its
sight draft accompanied by a certificate by Landlord (or its representative)
that Landlord is entitled to draw upon the same pursuant to provisions of this
Lease and (iv) by its terms shall not expire prior to the first year anniversary
of the Commencement Date. At least thirty (30) days prior to the expiration of
the Letter of Credit, Tenant shall deliver to Landlord one of the following (i)
cash in an amount equal to the Security Deposit, (ii) an amendment to the letter
of credit extending the expiry date for an additional year or (iii) a new letter
of credit having an expiry date of at least one year from the date of expiration
of the existing letter of credit. Should Tenant deliver either a new letter of
credit or cash in lieu of the letter of credit, then, Landlord will return the
letter of credit to Tenant. The failure of Tenant to deliver Landlord an
extension of the letter of credit, a new letter of credit or cash in lieu of the
letter of credit, at least thirty (30) days prior to the expiration of the date
of the letter of credit Landlord is holding as a Security Deposit shall entitle
Landlord to draw upon the letter of credit and hold such proceeds pursuant to
the provisions of SECTION 23.01 hereof.


          SECTION 23.04.  CHANGES TO SECURITY DEPOSIT.

          Within five (5) business days after Landlord disburses any Tenant
Improvement Allowance to Tenant, Tenant shall increase the Security Deposit by
an amount equal to the disbursed Tenant Improvement Allowance amount (the
"ADDITIONAL SECURITY DEPOSIT"). Provided that there has been no monetary Default
or material non-monetary Default by Tenant under this Lease at the applicable
time, Tenant shall have the right to reduce the Additional Security Deposit by
twenty-five percent (25%) on the commencement date of each of the third Lease
Year, fourth Lease Year, fifth Lease Year and sixth Lease Year. However, in no
event shall the Security Deposit be reduced below $84,875.00.


                         PART 24 - INTENTIONALLY OMITTED


                   PART 25 - ATTORNEYS FEES AND LEGAL EXPENSES

          In any action or proceeding brought by either party against the other
under this Lease, the prevailing party shall be entitled to recover from the
other party reasonable attorneys fees, and other reasonable legal expenses and
court costs incurred by such party in such action or proceeding as the court may
find to be reasonable.


                                PART 26 - NOTICES

          Any notice, demand, request, consent, approval or other communication
which either party hereto is required or desires to give or make or communicate
to the other shall be in writing and shall be given or made or communicated by
United States registered or certified mail or by any overnight or express mail
service which provide receipts to indicate delivery, addressed to the


                                                                            C-26
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

parties hereto at the respective addresses specified in the Basic Lease
Information, or at such other address as they have subsequently specified by
written notice.

          All notices shall be effective upon being deposited in the manner
prescribed above, however, the time period in which a response to such notice
must be given shall commence to run from the date of receipt by the addressee
thereof as shown on the return receipt of the notice. Rejection or other refusal
to accept or the inability to deliver because of changed address of which no
notice was given, shall be deemed to be receipt of the notice as of the date of
such rejection, refusal or inability to deliver.


                             PART 27 - MISCELLANEOUS

          SECTION 27.01.  NO PARTNERSHIP.

          Nothing contained in this Lease shall be construed as creating a
partnership or joint venture of or between Landlord and Tenant, or to create any
other relationship between the parties hereto other than that of Landlord and
Tenant.


          SECTION 27.02.  BROKERS.

          Landlord recognizes the Broker as the Broker under this Lease and
shall pay the Broker a commission pursuant to a separate agreement between the
Broker and Landlord, Landlord and Tenant each represent and warrant to the other
that, except as provided above, neither of them has employed or dealt with any
broker, agent or finder in carrying on the negotiations relating to this Lease.
In the event of a breach by a party of their foregoing representation and
warranty (the "DEFAULTING PARTY"), the Defaulting Party shall indemnify and hold
the other party harmless from and against any claim or claims, damages or
expenses (including any claims for brokerage or other commissions asserted by
any broker, agent, or finder fees) which may arise as a result of such breach.


          SECTION 27.03.  SEVERABILITY.

          Every agreement contained in this Lease is, and shall be construed as,
a separate and independent agreement. If any term of this Lease or the
application thereof to any person or circumstances shall be invalid and
unenforceable, the remainder of this Lease, or the application of such term to
persons or circumstances other than those as to which it is invalid or
unenforceable, shall not be affected.


          SECTION 27.04.  TRIAL BY JURY.

          Landlord and Tenant each hereby waive trial by jury in any action,
proceeding or counterclaim brought by either of them against the other in
connection with any matter arising out of or in any way connected with this
Lease, the relationship of Landlord and Tenant hereunder, Tenant's use or
occupancy of the Premises, or any claim of injury or damage.


          SECTION 27.05.  FORCE MAJEURE.

          Whenever a period of time is herein prescribed for action to be taken
by Landlord, Landlord shall not be liable or responsible for, and there shall be
excluded from the computation for any such period of time, any delays due to
strikes, riots, acts of God, shortages of labor or materials, war, governmental
laws, regulations, or restrictions, or any other cause of any kind whatsoever
which is beyond the reasonable control of Landlord.


                                                                            C-27
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

          SECTION 27.06.  CAPTIONS.

          The article, part, and section headings contained in this Lease are
for convenience only and shall not enlarge or limit the scope or meaning of the
provisions hereof. Words of any gender used in this Lease shall include any
other gender, and words in the singular number shall be held to include the
plural, unless the context otherwise requires.


          SECTION 27.07.  BENEFIT AND BURDEN.

          If there be more than one Tenant, the obligations hereunder imposed
upon Tenant shall be joint and several, and all agreements and covenants herein
contained shall be binding upon the respective heirs, personal representatives,
successors, and, to the extent permitted under this Lease, assigns of the
parties hereto.


          SECTION 27.08.  NO REPRESENTATIONS BY LANDLORD.

          Neither Landlord nor Landlord's agents or brokers have made any
representations or promises with respect to the Premises or the Building except
as herein expressly set forth and all reliance with respect to any
representations or promises is based solely on those contained herein. No
rights, easements, or licenses are acquired by Tenant under this Lease by
implication or otherwise except as expressly set forth in this Lease.


          SECTION 27.09.  ENTIRE AGREEMENT.

          This Lease sets forth entire agreement between the parties and cancels
all prior negotiations, arrangements, brochures, agreements, and understandings,
if any, between Landlord and Tenant regarding the subject matter of this Lease.
No amendment or modification of this Lease shall be binding or valid unless
expressed in a writing executed by both parties hereto.


          SECTION 27.10.  NO OFFER.

          The submission of this Lease to Tenant shall not be construed as an
offer, nor shall Tenant have any rights with respect thereto unless said lease
is consented to by any lender and any lessor to Landlord, to the extent such
consent is required, and Landlord executes a copy of this Lease and delivers the
same to Tenant. Such consent shall be deemed to have been obtained if Landlord
executes a copy of this Lease and delivers the same to Tenant.


          SECTION 27.11.  AUTHORITY.

          If Tenant signs as a corporation, each of the persons executing this
Lease on behalf of Tenant represents and warrants that Tenant is a duly
organized and existing corporation, that Tenant has been and is qualified to do
business in the Commonwealth of Virginia, that the corporation has full right
and authority to enter into this Lease, and that all persons signing on behalf
of the corporation were authorized to do so by appropriate corporate actions. If
Tenant signs as a partnership, trust, or other legal entity, each of the persons
executing this Lease on behalf of Tenant represents and warrants that Tenant has
complied with all applicable laws, rules, and governmental regulations relative
to its right to do business in the Commonwealth of Virginia, that such entity
has the full right and authority to enter into this Lease, and that all persons
signing on behalf of the Tenant were authorized to do so by any and all
necessary or appropriate partnership, trust, or other actions.


                                                                            C-28
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

          SECTION 27.12.  CHANGES REQUESTED BY LENDER.

          If, in connection with obtaining financing for the Building, any
lender shall request reasonable modifications in this Lease as a condition for
such financing, Tenant will not unreasonably withhold, delay, or defer its
consent thereto, provided such modifications do not increase the obligations of
Tenant hereunder or materially adversely affect either the leasehold interest
hereby created or Tenant's use and enjoyment of the Premises.


          SECTION 27.13.  GOVERNING LAW AND CONSTRUCTION.

          This Lease shall be governed by and construed under the laws of the
Commonwealth of Virginia. This Lease consists of three (3) parts, the Basic
Lease, General Lease Provisions and Exhibits which are to be read together as a
complete integrated document. Printed parts of this Lease shall be as binding on
the parties hereto as other parts hereof. Parts of this Lease which are written
or typewritten shall have no greater force or effect than and shall not control
parts which are printed, but all parts shall be given equal effect. Tenant
declares that Tenant has read and understands all parts of this Lease, including
all printed parts thereof. Should any provision of this Lease require judicial
interpretation, it is agreed that the court interpreting or considering same
shall not apply the presumption that the terms hereof shall be more strictly
construed against a party by reason of the rule or conclusion that a document
should be construed more strictly against the party who itself or through its
agents prepared the same, it being agreed that all parties hereto have
participated in the preparation of this Lease and that each party had full
opportunity to consult with legal counsel of its choice before the execution of
this Lease.


          SECTION 27.14.  LANDLORD'S LIABILITY.

          Anything contained in this Lease to the contrary notwithstanding,
Tenant agrees that Tenant shall look solely to the estate and property of
Landlord in the Building and the land upon which is situated for the collection
of any judgment or other judicial process requiring the payment of money by
Landlord for any default or breach by Landlord under this Lease, subject,
however, to the prior rights of any mortgagee or lessor of the Building and land
upon which the Building is situated. No other assets of Landlord or any
partners, shareholders, or other principals of Landlord shall be subject to
levy, execution or other judicial process for the satisfaction of Tenant's
claim.


          SECTION 27.15.  USE OF NAME OF BUILDING.

          Tenant shall not, without prior written consent of Landlord, use the
name of the Building for any purpose other than as the address of the business
to be conducted by Tenant on the Premises, and Tenant shall not do or permit the
doing of anything in connection with Tenant's business or advertising which in
the reasonable judgment of Landlord may reflect unfavorably on Landlord or the
Building or confuse or mislead the public as to any apparent connection or
relationship between Tenant and Landlord, the Building or the land upon which it
is situated.


          SECTION 27.16.  CHANGES BY LANDLORD.

          Landlord shall have the unrestricted right to make changes to all
portions of Fair Lakes (of which the Building and land upon which it is situated
are a part) in Landlord's reasonable discretion for the purpose of improving
access of or security to Fair Lakes or the flow of pedestrian vehicular traffic
therein. Landlord shall be entitled to change the name or address of the
Building or Fair Lakes. Landlord shall have the right to close, from time to
time, the common areas of the land upon which the Building is situated, Fair
Lakes and other portions of Fair Lakes for such temporary periods as Landlord
deems legally sufficient to evidence Landlord's ownership and control thereof
and to prevent any claim of adverse possession by, or any implied or actual
dedication to the public or any party other than Landlord.


                                                                            C-29
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

          SECTION 27.17.  TIME OF ESSENCE.

          Time is of the essence in this Lease.


                                                                            C-30
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

                              EXHIBIT "D" TO LEASE

                                     BETWEEN

                           BUILDING IV ASSOCIATES L.P.
                                  ("LANDLORD")

                                       and

                       PERFORMANCE ENGINEERING CORPORATION
                                   ("TENANT")


                              RULES AND REGULATIONS


          This EXHIBIT "D" is attached to and made a part of that Office Lease
Agreement dated _____________________, 19___ (the "LEASE"), between BUILDING IV
ASSOCIATES L.P. ("LANDLORD"), and PERFORMANCE ENGINEERING CORPORATION,
("TENANT"). Unless the context otherwise requires the terms used in this Exhibit
that are defined in the Lease shall have the same meanings as provided in the
Lease.

          The following rules and regulations have been formulated for the
safety and well-being of all tenants of the Building and to ensure compliance
with governmental and other requirements. Any continuing violation of these
rules and regulations by Tenant shall constitute a Default by Tenant under the
Lease.

          Landlord may, upon request of any Tenant, waive compliance by such
Tenant with any of the following rules and regulations, provided (i) no waiver
shall be effective unless signed by Landlord; (ii) any such waiver shall not
relieve such Tenant from the obligation to comply with such rule or regulation
in the future unless otherwise agreed to by Landlord; (iii) no waiver granted to
any Tenant shall relieve any other tenant from the obligation of complying with
these rules and regulations, unless such other tenant has received a similar
written waiver from Landlord; and (iv) any such waiver by Landlord shall not
relieve Tenant from any liability to Landlord for any loss or damage occasioned
as a result of Tenant's failure to comply with any rule or regulation.

          1. Sidewalks, plaza areas, entrances, courts, elevators, stairways,
corridors and all other public areas of the Building shall not be obstructed or
encumbered by any tenant or used for any purpose other than ingress and egress
to and from the premises of such tenant.

          2. No awnings or other projections shall be attached to the outside
wall or windows of the Building. No curtains, blinds, shades, or screens (other
than those furnished by Landlord as Building Standard) shall be attached to or
hung in, or used in connection with, any window or door of the premises of any
tenant.

          3. No showcases or other articles shall be put in front of or affixed
to any part of the exterior of the Building, nor placed in the corridor, or
other public areas of the Building.

          4. Plumbing fixtures and appliances shall be used only for the
purposes for which they were constructed, and no sweepings, rubbish, rags, or
other substances (including, without limitation, coffee grounds) shall be thrown
therein. The cost of repairing any stoppage or damage resulting from misuse of
such fixtures by a tenant or such tenant's servants, employees, agents,
visitors, or licensees, shall be paid by such tenant.

          5. No tenant shall bring or keep, or permit to be brought or kept, any
inflammable, combustible, or explosive fluid, materials, chemical, or substance
in or about its premises.

          6. No tenant shall mark, paint, drill into, or in any way deface, any
part of the Building or its premises except for decorative purposes. No boring,
cutting, or stringing of wires shall be permitted.


                                                                             D-1
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

          7. No cooking shall be done or permitted in the Building by any
tenant, except for that which is consistent with an employee kitchen within the
premises. No tenant shall cause or permit any unusual or objectionable odors to
emanate from its premises.

          8. Neither the whole nor any part of the premises of any tenant shall
be used for manufacturing, for the storage of merchandise, or for the sale or
exchange of merchandise, goods, or property of any kind.

          9. Tenants shall not construct, maintain, use, or operate within their
respective premises any electrical device, wiring, or apparatus in connection
with a loud-speaker system or other sound system, except as reasonably required
as part of a communication system approved prior to the installation thereof by
Landlord. No such loud-speaker system shall be constructed, maintained, used or
operated outside of the premises.

          10. No tenant shall make, or permit to be made, any unseemly or
disturbing noises or disturb or interfere with other tenants or occupants of the
Building or neighboring buildings whether by the use of any musical instrument,
radio, television, or other audio device, whistling, singing, or in any other
way. Nothing shall be thrown out of any doors, windows, or any passageways.

          11. No  additional locks or bolts of any kind shall be placed upon any
of the doors or windows by and tenant, nor shall any changes be made in any
existing locks or the locking mechanisms therein, without Landlord's approval.
The doors leading to the corridors or main halls shall be kept closed during
business hours except as they may be used for ingress or egress. Each tenant
shall, upon the termination of its tenancy, restore to Landlord all keys of
offices and storage and toilet rooms either furnished to, or otherwise procured
by, such tenant. In the event of the loss of any keys so furnished, such tenant
shall pay to Landlord the replacement cost thereof.

          12. The normal hours of operation of the Building shall be 7:00 a.m.
to 6 p.m. Monday through Friday, and 8 a.m. to 1 p.m. on Saturdays, customary
legal holidays excluded.

          13. No tenant shall use or occupy or permit any portion of its
premises to be used or occupied as an employment bureau or for the storage,
manufacture, or sale of liquor, narcotics, or drugs. No tenant shall engage or
pay any employees in the Building, except those actually working for such tenant
in the Building, nor advertise for laborers giving an address at the Building.

          14. Landlord reserves the right to exclude from the Building at all
times any person who is not known or does not properly identify himself to the
Building management or watchman on duty, Landlord may at its option, require all
persons admitted to or leaving the Building between the hours of 6 p.m. and 7:30
a.m., Monday through Friday, and at any hour on Saturdays, Sundays, and legal
holidays, to register. Each Tenant shall be responsible for all persons for whom
it authorizes entry into the Building, and shall be liable to Landlord for all
acts or omissions of such persons.

          15. Each  tenant, before closing and leaving its premises at any time,
shall lock all entrance doors and turn off all lights and electrical appliances.

          16. No premises shall be used, or permitted to be used, for lodging or
sleeping or for any immoral or illegal purpose.

          17. Landlord's employees shall not perform, and shall not be requested
by any tenant to perform, any work outside of their regular duties, unless under
specific instructions from the office of Landlord. The requirements of tenants
will be attended to only upon application to Landlord, and any such special
requirements shall be billed to tenants (and paid when the next installment of
rent is due) in accordance with the schedule of charges maintained by Landlord
from time to time or at such charge as is agreed upon in advance by Landlord and
such tenant.

          18. Canvassing, soliciting, and peddling in the Building are
prohibited, and each tenant shall cooperate in seeking their prevention.


                                                                             D-2
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

          19. No animals of any kind shall be brought into or kept about the
Building by any tenant.

          20. No vending machines for commercial or public use shall be
permitted to be placed or installed in any part of the Building by any Tenant.
Tenant may have vending machines in kitchen or other non-public areas of the
Premises so long as (i) such machines are not available for use by the general
public; (ii) Landlord has approved such machines and (iii) the machines are not
visible to the exterior of the Premises or the Building. Landlord reserves the
right to place or install vending machines in any of the public areas of the
Building.

          21. No plumbing or electrical fixtures shall be installed by any
Tenant without the written consent of Landlord.

          22. Bicycles, motorcycles, or any other type of vehicle shall not be
brought into the lobby or elevators of the Building or into the premises of any
tenant.

          23. Landlord has the right to evacuate the Building in event of
emergency or catastrophe.

          24. Landlord shall have the right, exercisable without notice and
without liability to any tenant, to change the name and street address of the
Building.

          25. Landlord reserves the right to rescind any of these Rules and
Regulations and make such other and further rules and regulations as in the
judgment of Landlord shall from time to time be needed for the safety,
protection, care, and cleanliness of the Building, the operation thereof, the
preservation of good order therein, and the protection and comfort of its
tenants, their agents, employees, and invitees, which Rules and Regulation when
made and notice thereof given to a Tenant shall be binding upon him in like
manner as if originally herein prescribed.


                                                                             D-3
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

                                   EXHIBIT "E"

                     Right of First Refusal and Offer Letter


                                [TO BE ATTACHED.]


                                                                             E-1
                                      Initials:  _____ (Landlord) _____ (Tenant)


<PAGE>

                                   EXHIBIT "F"

             Non-Disturbance, Subordination and Attornment Agreement


                                [TO BE ATTACHED.]


                                                                             F-1
                                      Initials:  _____ (Landlord) _____ (Tenant)