<PAGE>
                                                               Exhibit 10.19

                                  OFFICE LEASE

                                     BETWEEN

                          NEW ALLIANCE PROPERTIES, INC.
                             a Delaware corporation

                                   "LANDLORD"

                                       AND

                               LIGHTBRIDGE, INC.,
                             a Delaware corporation

                                     TENANT

                                  FOR SPACE AT
                              THE BUILDING KNOWN AS

                            295 INTERLOCKEN BOULEVARD

                             Dated: October 4, 1999
<PAGE>

                                                                         Page
                                                                         ----

                                TABLE OF CONTENTS

                                  OFFICE LEASE

                                                                         Page
                                                                         ----

1.     PREMISES; BUILDING; BUILDING COMPLEX; COMMON AREAS ..............    3

2.     LEASE TERM ......................................................    3

3.     RENT; SECURITY DEPOSIT ..........................................    3
       A.    Base Rent .................................................    3
       B.    Security Deposit ..........................................    3

4.     TENANT FINISH AND ACCEPTANCE OF THE PREMISES ....................    4
       A.    Landlord's Work ...........................................    4
       B.    Postponement of Lease Commencement Date ...................    4
       C.    Acceptance of Premises ....................................    4
       D.    Partial Months; Lease Commencement Certificate ............    4

5.     OPERATING EXPENSES ..............................................    4
       A.    Definitions Regarding Operating Expenses ..................    4
       B.    Payment of Operating Expenses .............................    7
       C.    Partial Years .............................................    7
       D.    Survival of Tenant's Obligation ...........................    7
       E.    Tenant's Right to Question Operating Expenses .............    7
       F.    Operating Expense Adjustments .............................    8

6.     TENANT'S EXPENSES ...............................................    8

7.     SERVICES ........................................................    8
       A.    Landlord's Services .......................................    8
       B.    Additional Services to Tenant .............................    8
       C.    Interruption of Services ..................................    8
       D.    Notice to Landlord ........................................    8
       E.    Year 2000 Compliance ......................................    9

8.     QUIET ENJOYMENT .................................................    9

9.     USE AND OCCUPANCY ...............................................    9

10.    MAINTENANCE AND REPAIRS .........................................    9
       A.    Landlord's Obligations ....................................    9
       B.    Tenant's Obligations ......................................   10

11.    ALTERATIONS AND ADDITIONS .......................................   10
       A.    Alterations by Tenant .....................................   10
       B.    Ownership and Removal of Alterations ......................   11
       C.    Landlord's ADA Alterations ................................   11

12.    ENTRY BY LANDLORD ...............................................   11

13.    MECHANICS LIENS .................................................   12


                                       i
<PAGE>

                                                                         Page
                                                                         ----

14.    SUBLETTING AND ASSIGNMENT .......................................   12
       A.    Tenant's Right ............................................   12
       B.    Other Restrictions; What Constitutes an Assignment ........   13
       C.    Certain Subleases .........................................   13
       D.    Related Corporation Assignment.............................   13

15.    DAMAGE TO PROPERTY; CLAIMS ......................................   14
       A.    Landlord Not Liable .......................................   14
       B.    Tenant's Indemnity ........................................   14

16.    INSURANCE .......................................................   14
       A.    Landlord's Insurance ......................................   14
       B.    Tenant's Insurance ........................................   14
       C.    Waiver of Claims and Subrogation ..........................   15

17.    DAMAGE OR DESTRUCTION TO BUILDING ...............................   15
       A.    Repair of Damage ..........................................   15
       B.    Termination of Lease ......................................   15

18.    CONDEMNATION ....................................................   16

19.    ESTOPPEL CERTIFICATE ............................................   16
       A.    Duty to Provide ...........................................   16
       B.    Tenant's Failure to Deliver ...............................   16

20.    DEFAULT BY TENANT ...............................................   17
       A.    Event of Default ..........................................   17
       B.    Remedies of Landlord ......................................   17
       C.    Late Charges and Interest .................................   19
       D.    Mitigation ................................................   19
       E.    No Waiver .................................................   19
       F.    Landlord's Lien ...........................................   19

21.    SUBORDINATION AND ATTORNMENT ....................................   20
       A.    General ...................................................   20
       B.    Lease Modifications .......................................   20

22.    SURRENDER AND HOLDING OVER ......................................   20
       A.    Surrender .................................................   20
       B.    Property Not Removed ......................................   20
       C.    Holding Over ..............................................   20

23.    LANDLORD DEFAULT ................................................   21

24.    NOTICE ..........................................................   22

25.    RULES AND REGULATIONS ...........................................   22

26.    PARKING .........................................................   22

27.    RIGHT TO RELOCATE TENANT ........................................   22

28.    MISCELLANEOUS ...................................................   22
       A.    Limitation of Landlord's Liability ........................   22
       B.    No Merger .................................................   22


                                       ii
<PAGE>

                                                                         Page
                                                                         ----

       C.    Landlord's Use of Common Areas ............................   22
       D.    Covenants are Independent .................................   23
       E.    Severability ..............................................   23
       F.    Captions and Terms ........................................   23
       G.    Binding Effect; Governing Law .............................   23
       H.    Tenant's Authority ........................................   23
       I.    Joint and Several .........................................   23
       J.    Acts Binding Landlord .....................................   23
       K.    Change in Light or View ...................................   23
       L.    No Other Agreements; Amendments ...........................   23
       M.    Brokers ...................................................   24
       N.    Recordation ...............................................   24
       O.    Execution Required ........................................   24
       P.    Attorney's Fees ...........................................   24
       Q.    Time of Essence; Effective Dates ..........................   24

29.    OPTION TO EXTEND ................................................   24
       A.    Exercise of Option.........................................   24
       B.    Rent Determination.........................................   24


30.    RIGHT OF FIRST OFFER ............................................   26
       A.    Exercise ..................................................   26
       B.    No Default ................................................   27

31.    SIGNAGE .........................................................   27

32.    FUEL TANK/UNINTERRUPTED POWER SOURCE ............................   27

Exhibits;

EXHIBIT A - Floor Plan of Leased Premises
EXHIBIT A-1 - Offer Space
EXHIBIT B - Legal Description of Building
EXHIBIT C - Tenant Improvement Agreement (Work Letter)
EXHIBIT D - Rules and Regulations
EXHIBIT E - Lease Commencement Certificate


                                      iii
<PAGE>


                                  OFFICE LEASE

                                     PART I

                             BASIC LEASE TERM SHEET

BUILDING:   295 Interlocken Boulevard, Broomfield, Colorado 80021.

LEASE DATE: October 4, 1999

LANDLORD:   New Alliance Properties, Inc., a Delaware corporation
            12800 Whitewater Drive, Suite 170
            Minnetonka, MN 55343

TENANT:     Lightbridge, Inc., a Delaware corporation

            Address: 295 Interlocken Boulevard, Suite 200
            Broomfield, Colorado 80021

            With a copy to: 67 S. Bedford St
            Burlington, MA 01803
            Attn:President or General Counsel

BUILDING MANAGER:       The Highline Group
                        1425 Market Street, Suite 205
                        Denver, Colorado 80202

LANDLORD'S BROKER:      Cushman Realty Corporation

TENANT'S BROKER:        Frederick Ross Company

PREMISES:               Suite Number: 200
                        295 Interlocken Boulevard
                        Broomfield, Colorado 80021

                   Tenant's Rentable Area: 16,034 RSF Premises

LEASE TERM: Lease Commencement Date: The earlier to occur of: (a) the date the
                                     Premises are Substantially Complete (as
                                     defined in the Work Letter); or (b)
                                     December 1, 1999

            Lease Expiration Date: Anticipated as December 31, 2004

            Lease Term: Commencement Date to Expiration Date (i.e.,
                        approximately 5 years plus 1 month)

<PAGE>

BASE RENT: Payable in monthly installments as follows:

      Period          Monthly            Per Sq. Ft.    Periods
      ------          -------            -----------    -------

Month 1               $18,038.25         $13.50         See Paragraph
                                                             3.A
Months 2-13           $18,038.25         $13.50         $216,459.00
Months 14-25          $18,492.55         $13.84         $221,910.56
Months 26-37          $18,946.84         $14.18         $227,362.12
Months 38-49          $19,427.86         $14.54         $233,134.36
Months 50-61          $19,908.88         $14.90         $238,906.60

TENANT'S PRO RATA SHARE: 25.06%

SECURITY DEPOSIT: $19,000.00

PARKING SPACES: Number of Parking Spaces: 64 surface parking spaces (i.e., 4
                spaces per 1,000 rentable square feet leased) at no cost to
                Tenant.

OPTIONS: See Paragraphs 29 & 30 below

GUARANTOR: None

THIS BASIC LEASE TERM SHEET, together with the General Provisions in Part II and
any Exhibits as Part III, all constitute the entire lease between Tenant and
Landlord for the Leased Premises, made and entered into as of the Lease Date.


                                       2
<PAGE>

                                     PART II
                               GENERAL PROVISIONS

      1. PREMISES; BUILDING; BUILDING COMPLEX; COMMON AREAS. In consideration of
the payment of the Rent and the performance of Landlord and Tenant's obligations
under the Lease, Landlord hereby leases to Tenant and Tenant leases from
Landlord the premises as described on the Basic Lease Term Sheet and as depicted
on Exhibit A (the "Premises") located in the building on the land described on
Exhibit B (the "Building"), together with a non-exclusive right to use all
common areas designated by Landlord for non-exclusive use of the tenants of the
Building. The Building, real property, landscaped and parking areas, drives and
related easements, common areas, and appurtenances are hereinafter collectively
sometimes called the "Building Complex" whether all or a part of it. The "Common
Areas" include the Building entrances, walkways, driveways to the Building,
stairways, common lobbies and corridors, electrical and telephone rooms, and
other areas designated from time-to-time by Landlord for the use of all tenants
of the Building.

      All entry of the Premises or Building Complex during construction under
the Work Letter (defined in Paragraph 4) by Tenant its employees, architects,
agents or representatives shall be at Tenant's sole risk, and Tenant shall
indemnify and hold Landlord and its employees, partners, contractors, and
Building Manager harmless from and against any and all injuries, death, damages,
loss, claims, suits and liability arising out of any such inspection, except to
the extent caused by the gross negligence or willful misconduct of Landlord, its
agents or employees. Tenant shall, subject to all conditions and terms of this
Lease exclusive of the payment of Rent, have access to the Premises prior to
lease commencement for the purposes of completion of the Tenant Work, as set
forth in the Work Letter attached hereto, installing phones, cabling and
furniture, however, Tenant shall not prior to the Lease Commencement Date,
occupy the Premises or permit others to do so, for any other purpose.

      2. LEASE TERM. The term of the Lease shall commence at 12:01 a.m. on the
Lease Commencement Date and shall terminate at 12:00 midnight on the Lease
Expiration Date, as specified on the Basic Lease Term Sheet (the "Primary Lease
Term"). The Primary Lease Term, as it may be extended, is referred to as the
"Lease Term."

      3. RENT; SECURITY DEPOSIT.

            A. Base Rent. Tenant shall pay to Landlord base rent for the
Premises ("Base Rent") as specified on the Basic Lease Term Sheet during the
Primary Lease Term. All installments of Base Rent shall be payable in advance,
on the first day of each calendar month during the Lease Term, except that the
first monthly installment of Base Rent which Tenant shall be obligated to pay
hereunder, shall be due and payable upon execution of this Lease by Tenant. All
Base Rent and Additional Rent (as hereinafter defined), (collectively, "Rent")
shall be paid without notice, demand, deduction, offset, or abatement (except as
otherwise expressly provided in this Lease), at Landlord's address or at such
other place as Landlord from time-to-time designates in writing. In no event
will the total Rent to be paid by Tenant during any Lease Year ever be less than
the Base Rent plus Tenant's Pro Rata Share of Operating Expenses under Paragraph
5. Notwithstanding anything to the contrary set forth herein, Tenant may occupy
the Premises and payment of Base Rent and Tenant's Pro Rata Share of Operating
Expenses shall be abated for a period commencing on the Commencement Date and
terminating on the last day of the first month of the Lease Term (the "Abatement
Rent Period"). If at any time during the Primary Term, an Event of Default
occurs, Tenant owes Landlord, in addition to all other amounts, Base Rent and
Tenant's Pro Rata Share of Operating Expenses abated pursuant to this Paragraph
during the Abatement Rent Period. Tenant, however, has no obligation to pay the
abated amounts if no Event of Default occurs prior to the expiration of the
Primary Term.

            B. Security Deposit. It is agreed that Tenant, concurrently with the
execution of this Lease, shall deposit with Landlord, and shall keep on deposit
at all times during the Lease Term, the security deposit specified on the Base
Lease Term Sheet (the "Security Deposit") as security for the payment by Tenant
of the Rent and for the faithful performance of all other provisions of this
Lease which are to be performed by Tenant. If, at any time during the Lease
Term, Tenant shall be in default


                                       3
<PAGE>

in the performance of any provision of this Lease, Landlord shall have the
right, but shall not be obligated, to use the Security Deposit, or so much as
necessary, in payment of any Rent or in performance of Tenant's other
obligations under this Lease, and in payment of any damages incurred by the
Landlord by reason of Tenant's defaults, which shall not waive or cure any such
default. In that event, Tenant shall, on written notice of Landlord, forthwith
remit to Landlord a sufficient amount in cash to restore the Security Deposit to
its original amount. The Security Deposit which has not been so utilized, shall
be refunded to Tenant, without interest, within 60 days after the termination of
this Lease upon full performance of this Lease by Tenant and vacation and
surrender of the Premises by Tenant as required by this Lease. Landlord shall
not be obligated to hold the Security Deposit in a segregated account and Tenant
shall be entitled to no interest on it. Landlord may deliver the Security
Deposit to or credit the Security Deposit to the purchase price paid by any
purchaser of Landlord's interest in the Premises, and thereupon Landlord shall
be discharged from further liability with respect to the Security Deposit. If a
Mortgagee (as hereinafter defined) succeeds to Landlord's interest by
foreclosure or deed in lieu, Tenant shall have no claim against Mortgagee unless
Mortgagee actually received the Security Deposit from Landlord. Tenant's
obligations under this Lease exceed the amount of the Security Deposit, Tenant
shall remain liable for the balance of its obligations.

      4. TENANT FINISH AND ACCEPTANCE OF THE PREMISES.

            A. Landlord's Work. Except as set forth in the Work Letter, Landlord
shall have no obligations for any remodeling or other work in the Premises, and
Tenant shall accept the Premises in their "as-is" condition on the date hereof.

            B. Postponement of Lease Commencement Date. [Intentionally Omitted]

            C. Acceptance of Premises. Following Tenant's completion of the
Tenant Improvements, taking possession of the Premises by Tenant shall be
conclusive evidence that the Premises and the Tenant Improvements are
Substantially Complete.

            D. Partial Months: Lease Commencement Certificate. If the
Commencement Date does not begin on the first day of a month, Tenant shall pay
proportionate Rent in advance for the partial month and the partial month shall
be considered part of the first Lease Year (as defined in subparagraph 5.A). In
the event the Commencement Date is delayed, the Lease Expiration Date shall be
extended so that the Primary Lease Term will continue for the full period set
forth in the Basic Lease Term Sheet. At the request of either party, Landlord
and Tenant shall execute a Lease Commencement Certificate, the form of which is
attached hereto as Exhibit E setting forth among other things the Lease
Commencement Date and the Lease Expiration Date.

      5. OPERATING EXPENSES.

            A. Definitions Regarding Operating Expenses. The following terms
have the following meanings with respect to their use in this Lease:

                  (1) "Building Rentable Area" means 63,995, which is the total
rentable square footage of the Building. If there is a significant change in the
Building Rentable Area as a result of an addition to the Building, partial
destruction, modification to building design, or similar cause which causes a
reduction or increase thereto on a permanent basis, Landlord shall make such
adjustments in the computations as shall be necessary to provide for any such
change.

                  (2) "Tenant's Pro Rata Share" means the percentage specified
on the Basic Lease Term Sheet. In the event Tenant, at any time during the Lease
Term, leases additional space in the Building, Tenant's Pro Rata Share shall be
recomputed by dividing the total rentable square footage of space then being
leased by Tenant (including any additional space) by the Building Rentable Area,
and the resulting percentage figure shall become Tenant's Pro Rata Share.


                                       4
<PAGE>

                  (3) "Lease Year" means each calendar year during the Lease
Term, except that the first Lease Year shall begin on the Lease Commencement
Date and end on December 31 of that year, and the last Lease Year shall begin on
January 1 of the calendar year in which this Lease expires or is terminated and
end on the date it expires or terminates. If the first or last Lease Year is
less than 12 months, Operating Expenses for these years shall be prorated.

                  (4) "Operating Expenses" means all operating expenses of any
kind or nature as reasonably determined by Landlord and which are incurred in
connection with the ownership, operation and maintenance of the Building
Complex. Operating Expenses shall include, but not be limited to:

                        (a) All real property taxes and assessments levied
against the Building Complex by any governmental or quasi-governmental
authority, including any taxes, assessments, reassessments, surcharges,
imposition, or under any covenants, declarations, easements or restrictions, or
other service, tax or other fees of a nature now in effect or which shall
hereafter be levied on the Building Complex as a result of the use, ownership or
operation of the Building Complex or for any other reason, whether in lieu of or
in addition to, any current real estate taxes and assessments; provided,
however, in no event shall the terms "taxes" or "assessments include any federal
or state income taxes levied or assessed on Landlord, nor transfer, conveyance,
franchise, estate or inheritance taxes, unless those taxes are a substitute for
real property taxes, nor interest or penalties assessed by reason of Landlord's
failure to pay taxes and assessments when due (collectively referred to as
"Taxes"). Expenses incurred by Landlord for tax consultants and in contesting
the amount or validity of any Taxes shall be included in such computations.
"Assessments" shall include general and special assessments, license tax,
business license fee, business license tax, commercial rental tax, levy, charge
penalty or tax, imposed by any authority having the direct power to tax,
including any city, county, state or federal government, or any school,
agricultural, lighting, water, drainage or other improvement or special
district, against the Premises, the Building or Building Complex or any legal or
equitable interest of Landlord therein. For the purposes of this Lease, any
special assessments shall be deemed payable in such number of installments as is
permitted by law, whether or not actually so paid;

                        (b) To the extent applicable, costs of cleaning (such as
exterior window cleaning) and other supplies, tools, materials and equipment
used in connection with the Common Areas;

                        (c) To the extent applicable, costs incurred in
connection with obtaining and providing energy for the Building Complex,
including costs of propane, butane, natural gas, steam, electricity, solar
energy and fuel oils, coal or any other energy sources as well as costs for
heating, ventilation, and air conditioning services ("HVAC"), exclusive of
electrical power for individual tenant spaces and associated rooftop HVAC units,
which shall be separately metered to each tenant;

                        (d) Costs of water and sanitary, storm drainage and
natural gas services for the Building Complex, exclusive of water for individual
tenant spaces associated with the operation of supplemental cooling and/or
Liebert unit(s), which shall be separately metered to each tenant;

                        (e) Costs of security services (if any) and janitorial
services (if any) for the Common Areas;

                        (f) Costs of maintenance, repairs, alterations,
improvements and replacements, including materials, labor, equipment and
maintenance contracts, but not costs of replacing buildings or structures; and

                        (g) Costs of maintenance and replacement of landscaping;
and costs of maintenance, repair, resurfacing, striping and repairing parking
areas and Common Areas, including trash, ice and snow removal;


                                       5
<PAGE>

                        (h) Insurance premiums in connection with the insurance
carried by Landlord in accordance with Paragraph 16, including fire and all-risk
coverage, together with loss of rent endorsement; the part of any claim required
to be paid under the deductible portion of any insurance policy carried by
Landlord in connection with the Building Complex; public liability insurance and
any other insurance carried by Landlord on the Building Complex;

                        (i) Labor costs limited to employees of the Landlord
directly associated with the building, including wages and other payments, costs
to Landlord of workmen's compensation and disability insurance, payroll taxes,
fringe benefits, pension, profit sharing and all legal fees and other costs or
expenses incurred in resolving any labor dispute;

                        (j) Professional building management fees and costs of
Building management space occupied by the Building Manager or its agents;
provided, that such professional building management fees shall be comparable to
management fees paid by landlords to property managers for comparable buildings
in the greater Metropolitan Denver market, from time to time;

                        (k) Legal, accounting, inspection, and consultation fees
(including fees charged by consultants retained by Landlord for services that
are designed to produce a reduction in Operating Expenses or to reasonably
improve the operation, maintenance or state of repair of the Building Complex)
incurred in the ordinary course of operating the Building Complex, but
specifically excluding legal fees incurred in connection with enforcement of any
lease or occupancy agreement in the Building Complex;

                        (l) The costs of capital improvements and structural
repairs and replacements made in or to the Building Complex or the cost of any
machinery or equipment installed in the Building Complex in order to conform to
any applicable laws, ordinances, rules, regulations or orders of any
governmental or quasi-governmental authority having jurisdiction over the
Building Complex ("Required Capital Improvement"); the costs of any capital
improvements and structural repairs and replacements designed primarily to
reduce Operating Expenses ("Cost Savings Improvements"). The expenditures for
Cost Savings Improvements shall be limited in any year to the amount of the
resulting reduction of Operating Expenses. Cost Savings Improvements and
Required Capital Improvements shall be amortized over their useful life of such
expenditure in accordance with generally accepted accounting principles;

                        (m) Any assessments, special assessments or other fees
or charges levied or imposed on the Building Complex by the Interlocken Owners
Association.

                  (5) "Operating Expenses" shall not include (i) costs of work,
including painting and decorating and tenant improvement work, which Landlord
performs for any tenant in the Building which is not for the benefit of all or
most tenants of the Building; (ii) costs of repairs or other work occasioned by
fire, windstorm or other insured casualty to the extent of insurance proceeds
received by Landlord, provided, that Landlord has obtained all insurance in the
form and amounts herein required under Paragraph 15A below; (iii) leasing
commissions, advertising expenses, legal expenses, and other costs incurred in
leasing space in the Building; (iv) costs of repairs or rebuilding necessitated
by condemnation; (v) any interest on borrowed money or debt amortization on
Landlord's mortgages on the Building, except as specifically set forth above;
(vi) depreciation on the Building; (vii) costs for janitorial services,
utilities or maintenance performed or paid for by tenants for their individual
premises; (viii) any cost incurred by the negligent acts or omissions of the
Landlord, its agents and employees; (ix) capital expenditures (except for Cost
Savings Improvements and Required Capital Improvements as permitted in 5.A
(4)(l) above); (x) payments for rented equipment, the cost of which equipment
would constitute a capital expenditure if the equipment were purchased except in
connection with Cost Savings Improvements and Required Capital Improvements;
(xi) costs incurred due to violation by the Landlord or any other tenant of the
Building Complex or any laws, rules, regulations or ordinances in effect on the
date hereof; or (xii) the cost of any work performed or service provided for
which the Landlord is otherwise reimbursed, to the extent so reimbursed.


                                       6
<PAGE>

            B. Payment of Operating Expenses. It is hereby agreed that, subject
to the provisions of Paragraph 3A above pertaining to the Abatement Rent Period,
commencing with the first Lease Year and continuing each month thereafter
through the Lease Term, Tenant shall pay to Landlord as Additional Rent at the
same time as Base Rent is paid an amount equal to 1/12 of Landlord's estimate of
Tenant's Pro Rata Share of the Operating Expenses for the particular Lease Year.
Landlord shall deliver to Tenant, as soon as practicable following the end of
any Lease Year, an estimate of the Operating Expenses for the new Lease Year
(the "Budget Sheet"). Until receipt of the Budget Sheet, Tenant shall continue
to pay its current monthly Tenant's Pro Rata Share of Operating Expenses based
upon the estimate for the preceding Lease Year. If the Budget Sheet reflects an
estimate of Tenant's Pro Rata Share of Operating Expenses for the new Lease Year
greater than the amount actually paid to the date of receipt of the Budget Sheet
for the new Lease Year, Tenant shall pay such amount to Landlord within 30 days
of receipt of the Budget Sheet. Upon receipt of the Budget Sheet, Tenant shall
thereafter pay the amount of its monthly Tenant's Pro Rata Share of the
Operating Expenses as set forth in the Budget Sheet. As soon as practicable
following the end of any Lease Year, but not later than May 1, Landlord shall
submit to Tenant a statement in reasonable detail describing the computations of
the Operating Expenses setting forth the exact amount of Tenant's Pro Rata Share
of the Operating Expenses for the Lease Year just completed, and the difference,
if any, between the actual Tenant's Pro Rata Share of the increase in Operating
Expenses for the Lease Year just completed and the estimated amount of Tenant's
Pro Rata Share of the Operating Expenses for such Lease Year (the "Statement").
Notwithstanding the foregoing, Landlord's failure to deliver the Statement to
Tenant on or before May 1 shall not be a waiver of Landlord's rights under this
Paragraph. If the actual Tenant's Pro Rata Share of the Operating Expenses for
the period covered by the Statement is higher than the estimated Tenant's Pro
Rata Share of the Operating Expenses which Tenant previously paid during the
Lease Year just completed, Tenant shall pay to Landlord the difference within 30
days following receipt of the Statement from Landlord. If the actual Tenant's
Pro Rata Share of the Operating Expenses for the period covered by the Statement
is less than the estimated Tenant's Pro Rata Share of the Operating Expenses
which Tenant previously paid during the Lease Year just completed, Landlord
shall credit the excess against any sums then owing or next becoming due from
Tenant under this Lease. In no event will Rent be less than Base Rent. In the
event the Building is not fully occupied during any particular Lease Year,
Landlord shall adjust those Operating Expenses which are affected by the
occupancy rates for the particular Lease Year, or part of it, as the case may
be, to reflect an occupancy of 95% percent of the Building Rentable Area.

            C. Partial Years. If the Lease Term covers a period of less than a
full calendar year during the first or last Lease Years, Tenant's Pro Rata Share
of the Operating Expenses for the partial year shall be calculated by
proportionately reducing Operating Expenses to reflect the number of months in
that year.

            D. Survival of Tenant's Obligation. Landlord's and Tenant's
responsibilities with respect to the Operating Expenses survive the expiration
or termination of this Lease and Landlord shall have the right to retain the
Security Deposit, or so much thereof as it deems necessary, to secure Tenant's
obligations attributable to the Lease Year in which this Lease terminates.

            E. Tenant's Right to Question Operating Expenses. If Tenant
questions the amount of Operating Expenses as shown by the Statement, Tenant
shall notify Landlord within 45 days after receipt of the Statement. If Tenant
does not give Landlord notice within that time period, Tenant shall have waived
its right to dispute the Statement. If Tenant timely gives notice, it shall have
90 days after giving notice to hire, at Tenant's sole expense, an accredited
member of the Colorado Society of CPA's ("Tenant's Accountants"), to examine
Landlord's books and records for the purpose of verifying the accuracy of the
Statement. If Tenant's Accountants determine that an error has been made, notice
describing the error in reasonable detail must be given to Landlord during that
90-day period, or the right to question the Statement shall be waived; and if
such a notice is given, Landlord and Tenant shall endeavor to agree upon the
matter within the following 30 days. All information disclosed to Tenant or
Tenant's Accountants in connection with any such review shall be kept
confidential by Tenant and Tenant's Accountants and shall not be disclosed or
used by Tenant or Tenant's Accountants for any reason other than to verify
information set forth in the Statement. Notwithstanding the pendency of


                                       7
<PAGE>

any dispute over any particular Statement, Tenant shall continue to pay Landlord
the amount of the adjusted monthly installments of Additional Rent based upon
the Statement until the dispute is resolved. Delay by Landlord in submitting any
Statement for any Lease Year shall not affect the provisions of this Paragraph
or constitute a waiver of Landlord's rights as set forth herein for that or any
subsequent Lease Year.

            F. Operating Expense Adjustments. Notwithstanding anything in this
Lease to the contrary, if any lease entered into by Landlord with any tenant in
the Building is on a "pure net" basis, or provides for a different basis of
computation for any Operating Expenses with respect to its leased premises,
then, to the extent that Landlord determines that an adjustment should be made
in making the computations of Operating Expenses under this Lease, Landlord may
modify the computation of Building Rentable Area and Operating Expenses for any
Lease Year in order to eliminate or otherwise modify any such expenses which are
paid for in whole or in part by that tenant. Furthermore, Landlord shall also be
permitted to make such adjustments and modifications to the provisions of this
Paragraph as shall be reasonably necessary to achieve the intent of this Lease
or the intention of the parties hereto, provided that no such adjustments or
modifications which have the effect of increasing Tenant's obligations hereunder
shall be made without Tenant's prior consent.

      6. TENANT'S EXPENSES. Notwithstanding anything contained in this Lease to
the contrary, Tenant shall be responsible, at Tenant's sole cost and expense, to
arrange and pay for the janitorial services for the Premises and to arrange and
pay directly to the electrical service provider for all costs of all electrical
services associated with the operation and occupancy of the Premises, such as
lighting and electrical outlets and the HVAC serving the premises. As more
specifically provided in the Work Letter attached hereto as Exhibit C, Landlord
shall be responsible for the installation of a separate utility meters for
purposes of segregating the electrical power supply to the Premises. Said
separate meters to include the segregation of power supply necessary to operate
the HVAC system for the Premises.

      7. SERVICES.

            A. Landlord's Services. Subject to the provisions of subparagraph
7D, Landlord in accordance with standards established by Landlord from time to
time for the Building, agrees: (1) to furnish running water for use in Common
Area lavatories and drinking fountains, if any; and (2) to provide limited
janitorial services for the Building (including window washing of the outside of
exterior windows as may, in the judgment of Landlord, be reasonably required).

            B. Additional Services to Tenant. If Tenant requires other services
in addition to those required to be provided to all other tenants of the
Building, Tenant shall pay for those services monthly as Additional Rent. In
addition, Tenant shall pay as Additional Rent monthly with Base Rent any and all
charges for utility services supplied and materials furnished directly to the
Premises. It is also understood and agreed that Tenant shall pay the cost of
replacing light bulbs and/or tubes and ballast used in all lighting in the
Premises.

            C. Interruption of Services. Landlord may discontinue, reduce, or
curtail the Landlord's Services at such times as it may be necessary by reason
of accident, repairs, alterations, improvements, strikes, lockouts, riots, acts
of God, application of Laws (as hereinafter defined) or due to any other
happening beyond the control of Landlord. In the event of any interruption,
reduction, or discontinuance of Landlord's services Landlord shall, if possible,
give advance notice to Tenant, but Landlord shall not be liable for damages to
Tenant or any other party as a result thereof nor shall the occurrence of any
such event in any way be construed as an eviction of Tenant, cause or permit an
abatement, reduction or set off of Rent, or operate to release Tenant from any
of Tenant's obligations under this Lease.

            D. Notice to Landlord. Tenant shall promptly notify Landlord or the
Building Manager of any interruption in the Building services or of any defects
in the Building or Building systems of which Tenant becomes aware and of which
Landlord is not aware, including defects in pipes, electric


                                       8
<PAGE>

wiring, and HVAC equipment. In addition, Tenant shall provide Landlord with
prompt notification of any matter or condition of which it becomes aware which
may cause injury or damage to the Building, the Building Complex, or to any
person or property.

            E. Year 2000 Compliance. Landlord shall be responsible, at its sole
cost and expense, for taking all measures necessary to ensure that all Building
systems components which are owned and maintained by Landlord will accurately
process date and/or time data relating to the year 2000.

      8. QUIET ENJOYMENT. Subject to the provisions of this Lease, all Laws and
any mortgage, easement, covenants, reservations or other encumbrances on the
Building Complex, Landlord agrees to warrant and defend Tenant in the quiet
enjoyment and possession of the Premises during the Lease Term against any
person claiming under Landlord, so long as Tenant complies with its obligations
to pay Rent and performs all of its other obligations under this Lease.

      9. USE AND OCCUPANCY. The Premises shall be used and occupied as business
offices for the operation of Tenant's business (the "Permitted Use") and for no
other purpose, and Tenant shall use it in a careful, safe, and proper manner,
and pay on demand for any damage, including repair of damage, to the Building
Complex to the extent not covered by insurance proceeds actually received by
Landlord, caused by the use, act or neglect by Tenant, Tenant's agents or
employees, or any other person entering upon the Premises under express or
implied invitation of Tenant. Tenant shall at its sole cost, comply with all
applicable federal, state, city, quasi-governmental and utility provider laws,
statutes, ordinances, orders, codes, rules, regulations, covenants and
restrictions now or hereafter in effect, including the Americans With
Disabilities Act ("ADA") and all environmental laws (collectively referred to as
"Laws") applicable to Tenant's use, occupancy or alteration of the Premises, and
Tenant shall obtain all permits or licenses required for its business conducted
at the Premises. Tenant shall not commit waste or permit waste to be committed
or cause or permit any unpleasant odor or noise or other nuisance in or from the
Premises or on the Building Complex. Tenant shall not use the Premises for any
use that causes an increase in rates or cancellation of any insurance policy
covering the Building Complex. Tenant shall not store, keep, use, sell, dispose
of or offer for sale in, upon or from the Premises or the Building Complex any
article or substance prohibited by any insurance policy covering the Building
Complex or the Premises nor shall Tenant keep, store, produce, dispose of or
release on, in or from the Premises or the Building Complex (or allow others to
do so) any substance which may be deemed an infectious waste, hazardous waste,
hazardous or toxic material, or hazardous substance under any Laws (collectively
called "Hazardous Materials") except customary office and cleaning supplies
stored and used in accordance with Laws. Tenant represents and warrants to
Landlord that it shall not bring onto or allow other to bring any Hazardous
Materials onto the Building Complex, and that it has received no notice or
complaint from any governmental authority or third party that the business it
intends to operate in the Premises or that any property or materials it intends
to keep or allow on the Building Complex or in the Premises is a Hazardous
Material or violates any Laws. Tenant shall give prompt notice to Landlord of
any such notice or complaint it has received or does receive in the future.
Tenant shall pay when due any taxes assessed with respect to Tenant's use or
occupancy of the Premises and Tenant's Property (as defined in Paragraph 11) and
any Alterations made by Tenant.

      10. MAINTENANCE AND REPAIRS.

            A. Landlord's Obligations. Landlord shall, subject to reimbursement
as part of Operating Expenses, to the extent deemed reasonably necessary by
Landlord for operations of the Building Complex, repair and maintain in good
order and condition: the structural portions of the Building, plumbing, air
conditioning (including rooftop HVAC units), heating and electrical systems
installed or furnished by Landlord, the Building roof, the curtain wall,
including all glass connections at the perimeter of the Building, all exterior
doors, including any exterior plate glass within the Building, Building
telephone and electrical closets owned or operated by Landlord, Building
telephone and electrical closets, the Common Areas of the Building Complex,
landscaping, and interior portions of the


                                       9
<PAGE>

Building above and below grade which are not within space leased to Tenant or
other tenants in the Building. Landlord shall have no obligation to make
improvements to or to repair or maintain the Premises during the Lease Term.
Further, the parties acknowledge that the Tenant has engaged a consultant to
review the current condition of the Building's floor slab and said consultant
has made certain maintenance and repair recommendations. Landlord agrees to
review said recommendations with its consultant and to make those maintenance
and repairs, if any, which are necessary, in Landlord's commercially reasonable
judgment, to maintain the Building's floor slab in good condition and repair
which is at least comparable to its condition as of the date of this Lease, and,
to the extent Tenant reasonably believes Landlord has not complied with the
obligation to maintain the floor slab, and as a result the Premises has become
untenantable, Tenant may avail itself of the remedies set forth in Section 23.

            B. Tenant's Obligations. Tenant, at Tenant's sole cost and expense,
except for services furnished by Landlord pursuant to Paragraph 7 and Landlord's
obligations under Paragraph 10A, shall maintain, in good order, condition,
repair, and appearance the Premises, including the interior surfaces of the
ceilings (if damaged or discolored due in whole or in part to the act, neglect,
omission or fault of Tenant), windows, walls and floors, all doors, interior
glass partitions or glass surfaces (not exterior windows) and pipes, electrical
wiring, switches, fixtures and other special items exclusively serving the
Premises, subject to the provisions of Paragraph 15. In addition, Tenant shall
maintain, in good order, condition, repair and appearance the Fiber Optic Cable,
as defined in the attached Work Letter and all areas of the Building Complex
(including, but not limited to parking lot areas and landscape areas) affected
by the installation or use of the Fiber Optic Cable. Finally, Tenant shall
maintain, in good order, condition, repair and appearance of the UPS
Installation, as defined in Paragraph 32 below, and all areas of the Building
Complex (including, but not limited to the parking lot areas and landscape
areas) affected by the installation or use of the UPS Installation. In the event
Tenant fails to maintain the Premises as required by this Paragraph, Landlord
shall give Tenant notice to do such acts as are required by this Paragraph. If
within a reasonable time not to exceed 30 days following Landlord's notice,
Tenant fails to perform its obligations under this Paragraph, or if those
obligations cannot reasonably be completed within 30 days, fails to promptly
commence such work and diligently pursue it to completion within a reasonable
time not to exceed 90 days, then Landlord shall have the right, but shall not be
required, to do such acts and expend such funds at the expense of Tenant as are
reasonably required to perform those obligations, without curing Tenant's
default. The funds so expended plus 20% of such amounts as an overhead/
administrative charge shall be due and payable by Tenant within 10 days after
receipt of Landlord's invoice. Landlord shall have no liability to Tenant for
any damage, inconvenience or interference with the use of the Premises by Tenant
as a result of performing or not performing any such obligations.

      11. ALTERATIONS AND ADDITIONS.

            A. Alterations by Tenant. Except as expressly provided in the Work
Letter, Tenant shall make no alterations, additions or improvements to the
Premises or the Building Complex, (excluding items of a decorating nature such
as painting, carpeting, etc.) (the "Alterations"), including the installation of
equipment or machinery which requires modifications to existing electrical
outlets or increases Tenant's usage of electricity beyond the standard
electrical usage design for the Premises without obtaining the prior written
consent of Landlord, which shall not be unreasonably withheld or delayed. Tenant
shall submit any such request to Landlord at least 30 days prior to the
commencement of the Alterations. Landlord may impose, as a condition to its
consent, and at Tenant's sole cost such requirements as Landlord may reasonably
deem necessary in its judgment, including the manner in which the Alterations
are done, the material to be used, the architect and contractor by whom the work
is to be performed and the times during which the work is to be accomplished,
approval of all plans and specifications, and the procurement of all licenses
and permits. Landlord shall be entitled to or to require Tenant to post notices
on and about the Premises with respect to Landlord's non-liability for the
Alterations and Tenant shall not permit those notices to be defaced or removed.
Tenant further agrees not to connect any apparatus, machinery or device to the
Building systems, including electric wires, water pipes, fire, safety, heating
and mechanical systems, without the prior written consent of


                                       10
<PAGE>

Landlord, Alterations which Tenant is permitted to make shall be performed in a
good and workmanlike manner and in compliance with this Lease.

      If Landlord permits any Alterations, then prior to the commencement of
those Alterations, Tenant shall deliver to Landlord certificates (and copies of
the policies if requested by Landlord) issued by insurance companies qualified
to do business in the state where the Premises are located evidencing that
workmen's compensation, public liability insurance and property damage
insurance, builder's risk coverage (if applicable) all in amounts, with
companies and on forms satisfactory to Landlord, are in force and maintained by
all such contractors and subcontractors engaged by Tenant to perform the work.
All such policies shall name Landlord as an additional insured and shall provide
that they may not be canceled or modified without 30 days' prior notice to
Landlord.

      Tenant, at its sole cost and expense, shall cause any permitted
Alterations to be performed in compliance with all applicable requirements of
insurance policies, Laws, and governmental bodies having jurisdiction, in such
manner as not to interfere with other tenants or interfere with, delay, or
impose any additional expense upon Landlord in the construction, maintenance or
operation of the Building Complex, and so as to maintain harmonious labor
relations in the Building and to not disturb other tenants' use of their
premises or interfere with Landlord's operation of the Building Complex. In
addition, Tenant, at its sole cost and expense, shall be responsible for the
acquisition of auxiliary aids, required under the ADA, including all Alterations
required: (i) as a result of Tenant, or any subtenant, assignee or
concessionaire, being a Public Accommodation (as defined in the ADA); (ii) as a
result of the Premises being a Commercial Facility (as defined in the ADA);
(iii) as a result of any leasehold improvements made to the Premises by or on
behalf of Tenant, or any subtenant, assignee or concessionaire (whether or not
Landlord's consent to such leasehold improvements was obtained); or (iv) as a
result of the employment by Tenant, or any subtenant, assignee or
concessionaire, of any individual with a disability.

            B. Ownership and Removal of Alterations. All Alterations, whether
made by Landlord or Tenant, including all counters, screens, grilles, cabinetry
work, partitions, paneling, carpeting, drapes or other window coverings and
light fixtures (but not including Tenant's Property, as defined below), shall be
deemed a part of the real estate and the property of Landlord and shall remain
upon and be surrendered with the Premises without disturbance or injury, at the
end of the Lease Term, unless Landlord, by notice given to Tenant no later than
15 days after the end of the Lease Term or Tenant's possession, shall elect to
have Tenant remove all or any of the Alterations, and in that event, Tenant
shall promptly remove those Alterations. Any such removal, whether required or
permitted by Landlord, shall be at Tenant's sole cost and expense, and Tenant
shall restore and repair any damage caused by the removal. All movable
partitions, machines and equipment which are installed in the Premises by or for
Tenant, without expense to Landlord, which can be removed without damage to or
defacement of the Building or the Premises, and all unattached furniture,
furnishings and other articles of personal property owned by Tenant and located
in the Premises (all of which are herein called "Tenant's Property") shall be
and remain the property of Tenant and may be removed by it at any time during
the Lease Term, subject to the provisions of this Lease. However, if any of
Tenant's Property is removed, Tenant shall repair or pay the cost of repairing
any damage to the Building Complex or the Premises resulting from the removal.
Notwithstanding the foregoing, Landlord will make its election regarding removal
of Alterations at the time Landlord approves such Alterations if such election
by Landlord is expressly requested by Tenant at that time; provided, however,
that as to cabling, including any fiber optic or other cabling installed by
Tenant on the Property, the provisions of the first two sentences of this
Paragraph shall be applicable in all cases.

            C. Landlord's ADA Alterations. Landlord shall, subject to
reimbursement as part of Operating Expenses, be responsible for any alterations,
modifications or improvements to any Common Areas of the Building Complex which
are required by the ADA.

      12. ENTRY BY LANDLORD. Landlord, the Building Manager and their employees,
contractors and agents shall have the right to enter the Premises at all
reasonable times after twelve (12) hours advance notice to Tenant (except in the
case of an emergency) for the purpose of inspecting


                                       11
<PAGE>

it, to supply any services to be provided by Landlord, to show it to prospective
purchasers, investors or Mortgagees, to make such alterations, repairs,
maintenance, improvements or additions to the Premises or to the Building as
Landlord may deem necessary or desirable, and during the last 270 days of the
Lease Term or after an Event of Default to show it to prospective tenants.
Landlord may for these purposes, if Tenant is not present, enter the Premises by
means of a master key. Any such entry shall not entitle Tenant to an abatement
of Rent or any other claim against Landlord, except for Landlord's gross
negligence or willful misconduct.

      13. MECHANICS LIENS. Tenant has no right or authority to impose or permit
any lien or claim against the Premises, the Building, the Building Complex or
its interest in or under this Lease. Tenant shall pay all costs for work done by
or for Tenant in the Premises (including work performed by Landlord or its
contractor at Tenant's request following the commencement of the Primary Lease
Term) and Tenant will keep the Premises and the Building Complex free and clear
of all mechanics' and other liens on account of work done by or for Tenant or
persons claiming under it, excluding any Tenant Finish Work performed by
Landlord pursuant to the Work Letter. Tenant agrees to indemnify, defend, and
save Landlord harmless of and from all liability, loss, damage, costs, or
expenses, including attorneys' fees, on account of any claims of any nature
whatsoever for work performed or for materials or supplies furnished to Tenant
or persons claiming under Tenant. Should any such claims be made or liens be
recorded against the Premises, the Building or the Building Complex or should
any action affecting the title thereto be commenced as a result of any such
work, Tenant shall cause the claim to be satisfied before being recorded, or if
the claim or lien is recorded to be removed of record within ten days after
recording. If Tenant desires to contest any claim or lien, Tenant shall give
notice to Landlord of Tenant's intent to contest it and, within ten days after
the recording of any such liens, Tenant shall either furnish to Landlord
adequate security satisfactory to Landlord of at least 150% of the amount of the
claim, plus estimated costs and interest or bond over any lien under CRS
38-22-131 and as soon as possible thereby have the lien against the Premises,
Building and Building Complex discharged and released in full. If a final
judgment establishing the validity or existence of any lien for any amount is
entered, Tenant shall immediately pay and satisfy it. If Tenant fails to pay any
amount in the time periods provided herein, Landlord may (but without being
required to do so) pay such lien or claim and any costs, and the amount so paid,
plus 20% of such amounts as an overhead/administration charge, together with
reasonable attorneys' fees incurred in connection therewith, shall be
immediately due from Tenant to Landlord.

      14. SUBLETTING AND ASSIGNMENT.

            A. Tenant's Right. Tenant cannot assign this Lease or sublet all or
any part of the Premises without the prior written consent of Landlord, which
consent shall not be unreasonably withheld. If Tenant wants to assign this Lease
or sublet all or a portion of the Premises, Tenant shall first notify Landlord
in writing of the name of the proposed assignee or sub-tenant and the proposed
use of the Premises, and provide such financial and other information as
Landlord may reasonably require about the proposed assignee or subtenant. It
shall not be unreasonable for Landlord to withhold its consent to a proposed
assignment or sublease, including, if (i) the reputation, financial
responsibility, or business of the proposed assignee or subtenant is
unacceptable to Landlord; (ii) the intended use of the Premises by the proposed
assignee or subtenant either (a) is not similar to the use of the Premises
authorized by the provisions of this Lease or (b) violates any Laws or requires
modifications to the Premises or the Building Complex to comply with Laws unless
such modification is paid for by Tenant or Sub-Tenant and is installed pursuant
to and in compliance with Paragraph 11 above; (iii) if the proposed assignee or
subtenant is a present or former tenant of the Building, or (iv) the rent to be
paid by the proposed assignee or sublessee is no less than 85% of the Rent paid
by Tenant for that space or is less than 85% of the rental rate then being
offered by Landlord for similar space in the Building. Tenant shall have no
right to assign this Lease or sublet any part of the Premises if a notice of
default has been delivered by Landlord to Tenant, which default has not been
cured, or if an Event of Default exists under this Lease, either at the time of
Tenant's request for Landlord's consent to an assignment or sublease or at the
time the assignment or sublease is scheduled to commence.


                                       12
<PAGE>

            B. Other Restrictions; What Constitutes an Assignment. Any
assignment or subletting consented to by Landlord shall be in writing in a form
acceptable to Landlord. This Lease cannot be assigned or sublet by operation of
law. Any transfer of this Lease by a sale of all or substantially all of
Tenant's assets, merger, consolidation, liquidation, or change in ownership of
or power to vote the majority of outstanding stock of Tenant or, if Tenant is a
partnership, any withdrawal, replacement, or substitution of any partner or
partners, either general or limited, whether as the result of a single or series
of transactions, shall constitute an assignment for purposes of this Paragraph.
Any assignment or subletting shall not affect the liability of the Tenant under
this Lease or release Tenant from its obligations. Consent by Landlord to any
assignment or sublease shall not relieve the Tenant from the requirement of
obtaining the prior written consent of Landlord to any subsequent assignment or
subletting and Landlord's consent to one assignment or subletting shall not
waive Landlord's right to refuse to consent to a subsequent request. If Landlord
consents to Tenant's request to assign this Lease or sublet all or a portion of
the Premises, Tenant shall pay Landlord, at the time consent is given, in
consideration for Landlord's written consent to the assignment or sublease, an
amount equal to $500 as a subletting/assignment fee. In addition, Tenant or
Tenant's assignee or sublessee shall be solely responsible for all costs
incurred in altering the Premises to conform to Laws due to any change in the
intended use of the Premises. If Tenant collects any rent or other amounts from
an assignee or subtenant in excess of the Rent for any monthly period, Tenant
shall pay Landlord 50% of the excess monthly (after first deducting Tenant's
cumulative reasonable and direct costs related to the Transfer, including
commissions, or other reasonable costs, and tenant finish costs), as and when
received; and after a default by Tenant under this Lease, Landlord shall have
the right to collect any Rent directly from any subtenant (or from any assignee
from which is it not already collecting directly).

            C. Certain Subleases. Notwithstanding the above, if Tenant requests
Landlord's consent to sublet 25% or more of the Premises, Landlord may refuse to
grant consent in its sole discretion and may terminate this Lease as to that
portion of the Premises; provided, however, if Landlord does not consent and
elects to terminate the Lease as to that portion, Tenant may within 15 days
after notice from Landlord to this effect withdraw Tenant's request for consent.
If Landlord elects to terminate under this Paragraph, it shall be effective on
the date designated in a notice from Landlord, which shall be no later than the
proposed date of the sublease.

            D. Related Corporation Assignment. Notwithstanding anything to the
contrary set forth in this Section, and subject to all of the provisions of this
Lease, Tenant may assign this Lease to or permit any corporation or other
business entities which control, are controlled by, or are under common control
with Tenant (each, a "Related Corporation") to sublet the Premises for any of
the purposes permitted to Tenant under this Lease (subject, however, to
compliance with Tenant's obligations under this Lease) provided that (a) Tenant
shall not then be in default (after any applicable grace and/or cure periods in
the performance of any of its obligations under this Lease), (b) prior to such
assignment or subletting, Tenant furnishes Landlord with the name of any such
Related Corporation, together with the written certification of Tenant that such
entity is a Related Corporation of Tenant, and (c) in the reasonable judgment of
Landlord, the proposed assignee or subtenant is in keeping with the reasonable
standards of Landlord for the Building. Any such subletting shall not be deemed
to vest in any such Related Corporation any right or interest in this Lease or
the Premises nor shall any such subletting or assignment relieve, release,
impair or discharge any of Tenant's obligations hereunder. For the purposes
hereof, "control" shall be deemed to mean ownership of not less than 51% of all
of the legal and equitable interest in any other business entities. Further,
notwithstanding anything contained herein to the contrary, the provisions of
this Paragraph 13 shall not apply to transactions with a corporation into or
with which Tenant is merged or consolidated or to which substantially all of
Tenant's assets are transferred, provided that in any of such events the
successor to Tenant has a net worth computed in accordance with generally
accepted accounting principles at least equal to $10,000,000.00 and proof
satisfactory to Landlord of such net worth shall have been delivered to Landlord
at least ten (10) days prior to the effective date of any such transaction.


                                       13
<PAGE>

      15. DAMAGE TO PROPERTY; CLAIMS.

            A. Landlord Not Liable. Neither Landlord nor the Building Manager or
their employees or agents shall have any liability for, and Tenant shall neither
hold nor attempt to hold Landlord the Building Manager and their employees and
agents liable for any injury or damage, either proximate or remote, occurring
through or caused by fire, water, steam, or any repairs, alterations, injury,
accident, or any other cause to or within the Premises, to Tenant's Property or
other personal property of Tenant or others kept in the Premises or stored in
other parts of the Building and/or Common Areas, or for property of Tenant or
others entrusted to employees of the Building, or for loss of property by theft
or otherwise (including loss or damage in the parking areas) by reason of the
negligence or default of other occupants or any other person or otherwise, and
the keeping or storing of all property of Tenant in the Building, Common Areas
and/or Premises shall be at the sole risk of Tenant, unless caused by the
negligence or willful misconduct of Landlord.

            B. Tenant's Indemnity. Subject to provisions of Paragraph 16C,
Tenant hereby agrees to indemnify, defend, and save Landlord and Building
Manager harmless of and from all actions, suits, fines, penalties, liability,
loss, damages, costs, or expenses, including reasonable attorneys' fees,
resulting from Tenant's use or occupancy of the Premises, or on account of
injuries to the person or property of Tenant or any third party, including any
other tenant in the Building Complex or to any other person rightfully in the
Building Complex for any purpose whatsoever, where the injuries are caused by
the negligence, acts or misconduct of the Tenant, Tenant's agents, servants or
employees, or of any other person entering upon the Premises under express or
implied invitation of Tenant, or resulting from any breach of this Lease by
Tenant.

      16. INSURANCE.

            A. Landlord's Insurance. Landlord agrees to carry and maintain
commercial general liability insurance against personal injury, including death
and property damage, in or about the Building Complex (excluding Tenant's
Property), in such amounts as Landlord deems appropriate. Landlord shall
maintain casualty insurance for the Building Complex, the shell and core of the
Building and the Premises (other than the insurance Tenant is required to carry
on the Premises) in an amount equal to the full replacement cost of the Building
Complex, with endorsements for increased cost of construction and for demolition
costs, from such companies, and on such terms and conditions, including
insurance for loss of Rent, as Landlord deems appropriate from time to time.

            B. Tenant's Insurance. Tenant shall, at its own cost, at all times
during the Lease Term, procure and maintain workmen's compensation insurance in
the maximum statutory amount and Employers Liability insurance in the amount of
$500,000, each covering all persons employed by Tenant, insurance coverage at
least as broad as ISO Special Form Coverage against risks of direct physical
loss or damage (commonly known as "all risk") for the full replacement cost of
Tenant's Property and the contents of the Premises including damage due to water
leakage, in an amount equal to their full replacement cost, and commercial
general liability insurance, including coverage for bodily injury, property
damage, personal injury (employee and contractual liability exclusions deleted),
products and completed operations, contractual liability, owner's protective
liability, and broad form property damage with the following limits of
liability: $2,000,000.00 each occurrence combined single limit for bodily
injury, property damage and personal injury; $2,000,000.00 aggregate for bodily
injury and property damage for products and completed operations. All such
insurance shall be procured from a responsible insurance company or companies
authorized to do business in the State where the Premises are located, with
general policyholder's ratings of not less than AA + and a financial rating of
not less than "XI" in the most current available Best's Insurance Reports, and
shall be otherwise satisfactory to Landlord. All such policies (except workmen's
compensation) shall name Landlord and Building Manager as additional insureds,
and shall provide they cannot be canceled or altered except upon 30 days prior
written notice to Landlord. All insurance maintained by Tenant shall be primary
to any insurance carried by Landlord. If Tenant obtains any general liability
insurance policy on a claims-made basis, Tenant shall provide continuous
liability coverage for claims arising during the entire Lease Term, regardless
of when the claims are made, either by obtaining an endorsement providing for an
unlimited


                                       14
<PAGE>

extended reporting period in the event any such policy is canceled or not
renewed for any reason whatsoever or by obtaining new coverage with a
retroactive date the same as or earlier than the expiration date of the canceled
or expired policy. Tenant shall provide certificate(s), and if requested copies
of the policies, of such insurance to Landlord upon commencement of the Lease
Term and at least 30 days prior to their renewal date and such certificate(s)
and policies shall name Landlord and Building Manager as additional insureds, in
addition to the other requirements herein. The limits of Tenant's insurance
shall not, under any circumstances, limit the liability of Tenant under this
Lease.

            C. Waiver of Claims and Subrogation. Each party hereby waives and
releases the other party and its respective officers, directors, partners,
members, agents, representatives and employees, from any claim (including a
claim for negligence) which it might otherwise have against the other party for
loss, damage or destruction to its real and personal property (including the
Building, Building Complex, Premises and Tenant's Property) or for loss of
business arising out of or related to the use and occupancy of the Premises
occurring during the Lease Term which is insured or capable of being insured
against under insurance required under this Paragraph. Tenant also waives all
such rights of recovery against the Building Manager. Each party shall notify
its insurance carrier of this waiver provision and obtain an appropriate waiver
of subrogation provision in its policies

      17. DAMAGE OR DESTRUCTION TO BUILDING.

            A. Repair of Damage. In the event that the Premises or the Building
is damaged by fire or other insured casualty and insurance proceeds have been
made available to Landlord to repair the damage by the insurer and any
Mortgagees, the damage shall be repaired by and at the expense of Landlord to
the extent of the insurance proceeds, provided that the Premises can be made fit
for occupancy, in Landlord's reasonable opinion, within 180 days after the
occurrence of the damage without the payment of overtime or other premiums.
Until the repairs and restoration are completed, Rent shall be abated in
proportion to the part of the Premises which is unusable by Tenant in the
conduct of its business as the result of the casualty, as may be reasonably
determined by Landlord (but there shall be no abatement of Rent by reason of any
portion of the Premises being unusable for a period of five days or less or as
set forth below). Landlord agrees to notify Tenant within 60 days after the
casualty if it estimates that it will be unable to repair and restore the
Premises within 180 days, which will state the approximate length of time
Landlord estimates will be required to complete the repairs and restoration, in
which event Landlord in its notice or Tenant in a notice given to Landlord
within 15 days thereafter may terminate this Lease effective 30 days from the
date of such notice (the "Termination Date"). However, Tenant may not terminate
this Lease or receive an abatement of Rent, as above stated, if the damage to
the Premises or the Building is in whole or in part the result of the willful
act, omission, fault or negligence of Tenant, its agents or employees. In the
event this Lease is terminated, Tenant shall pay prorated Rent for the usable
portion of the Premises until the Termination Date and shall forthwith surrender
the Premises in accordance with Paragraph 22A. If Tenant fails so to surrender
the Premises, Landlord may reenter and take possession of the Premises and
remove Tenant and the property and Alterations Tenant is required to remove
under Paragraph 11, at Tenant's expense. Except as provided in this Paragraph,
there shall be no abatement of rent and no liability of Landlord by reason of
any damage to or interference with Tenant's business or property arising from
the casualty or the making of any such repairs, alterations or improvements in
or to the Building Complex or Premises. Tenant understands that Landlord will
not carry insurance of any kind on Tenant's Property, or any Alterations
installed in the Premises by or on behalf of Tenant, and that Landlord shall not
be obligated to repair any damage or replace any of Tenant's Property or any
such Alterations, which shall be Tenant's responsibility. In addition to
Tenant's right to terminate this Lease as provided above, Tenant shall have the
further right to terminate this Lease if the Premises shall not be fully
restored within 240 days after such damage, or if such damage shall occur within
the last 180 days of the Lease Term.

            B. Termination of Lease. In addition to the reason stated in
subparagraph A above, if the Building or Building Complex is substantially
damaged, to the extent that Landlord, in its reasonable judgment, determines
that it would be uneconomical to reconstruct or repair the damage (although the
Premises may not be affected, or if affected, can be repaired within 180 days)
and


                                       15
<PAGE>

Landlord, within 60 days after the damage, decides not to reconstruct or repair
the damage, then provided that Landlord contemporaneously terminates all leases
and other occupancies at the Building Complex, notwithstanding anything
contained herein to the contrary, upon notice to that effect given to Tenant
within that 60-day period, Tenant shall pay Rent, properly apportioned up to
date of such termination, and subject to abatement as provided herein, this
Lease shall terminate on the date provided in Landlord's notice of termination,
such termination date to be the earlier of (a) 30 days after such notice is
given or (b) 90 days after the date of casualty and both parties shall be
released and discharged from all further obligations hereunder (except those
obligations which expressly survive termination of the Lease Term). A total
destruction of the Building or the Building Complex shall automatically
terminate this Lease as of the date of the destruction.

      18. CONDEMNATION. If the entire Premises or substantially all of the
Premises or any portion of the Building Complex which shall render the Premises
untenantable shall be taken by eminent domain or by condemnation or shall be
conveyed in lieu of any such taking, then this Lease, at the option of either
Landlord or Tenant exercised by either party giving notice to the other of such
termination within 30 days after such taking or conveyance, shall as of the date
Tenant is dispossessed of the Premises terminate and the Rent shall be
apportioned as of that date; and Tenant shall surrender the Premises as required
in this Lease to Landlord and Landlord may reenter and take possession of the
Premises on that date. In the event less than all of the Premises shall be taken
by that proceeding, Landlord shall promptly repair the Premises as nearly as
possible to its condition immediately prior to the taking, unless Landlord
elects not to reconstruct or rebuild for the same reasons provided in Paragraph
17B. In the event of any such taking or conveyance, Landlord shall receive the
entire award or consideration for the portion of the Building or Building
Complex so taken. However, Tenant shall have the right to pursue its own reward,
so long as Tenant's reward does not in any way diminish Landlord's reward and
Tenant shall obtain Landlord's prior written concurrence that Landlord's award
will not be diminished before it may commence any such action.

      19. ESTOPPEL CERTIFICATE.

            A. Duty to Provide Tenant agrees at any time and from time to time
on or before seven days after written request by Landlord, to execute,
acknowledge and deliver to Landlord an estoppel certificate certifying (i) that
this Lease is unmodified and in full force and effect (or if there have been
modifications, that it is in full force and effect as modified, and stating the
modifications), (ii) that there have been no defaults by Landlord (to the best
of Tenant's knowledge) or by Tenant (or, if there have been defaults, describing
the default), (iii) the date to which Rent and other charges have been paid in
advance, if any, (iv) that Tenant claims no present charge, lien, claim or
offset against Rent if such is the case, (v) that Rent is not prepaid for more
than one month in advance, and (vi) such other matters as may be reasonably
required by Landlord, any Mortgagee or prospective Mortgagee, or any potential
purchaser of the Building. It is intended that any such statement delivered
pursuant to this Paragraph may be relied upon by any prospective purchaser of
all or any portion of Landlord's interest, or by any Mortgagee or prospective
Mortgagee.

            B. Tenant's Failure to Deliver. Tenant acknowledges that it may be
difficult, if not impossible, for Landlord to sell or finance the Building
without such an estoppel certificate from Tenant, and that Landlord would not
enter into this Lease without Tenant's agreement to provide such an estoppel
certificate. If Tenant shall fail to execute, acknowledge and deliver to
Landlord any estoppel on or before the expiration of the 7-day period provided
under Paragraph 19A above, Landlord shall again provide written request to
Tenant delivered in accordance with the provisions of Paragraph 24 below and if
Tenant fails to execute, acknowledge and deliver to Landlord such estoppel on or
before 7 days after said second request therefor, it shall be deemed both (1) as
Tenant's affirmation of the provisions of the estoppel, including that (a) this
Lease is in full force and effect, (b) there are no breaches or defaults on the
part of Landlord, and (c) no more than one month's rent has been paid in
advance; and (2) that Tenant has appointed Landlord as Tenant's attorney-in-fact
to execute said estoppel certificate in Tenant's stead and place.


                                       16
<PAGE>

      20. DEFAULT BY TENANT.

            A. Event of Default. Each one of the following events is referred to
as an "Event of Default":

                  (1) Any failure by Tenant to pay Rent on the due date unless
the failure is cured within 5 business days after notice by Landlord; however,
Tenant is not entitled to more than two notices of delinquent payments of Rent
during any calendar year and, if thereafter during that calendar year any Rent
is not paid when due, an Event of Default shall automatically occur;

                  (2) If Tenant's interest in this Lease or in the Premises, or
if all or a substantial part of Tenant's Property, is seized or taken by process
of law or otherwise and is not released within 15 days;

                  (3) Commencement by or against Tenant of a proceeding under
any provision of federal or state law relating to insolvency, bankruptcy, or
reorganization ("Bankruptcy Proceeding"), unless dismissed within 60 days after
commencement; the insolvency of Tenant or execution by Tenant of an assignment
for the general benefit of creditors; the convening by Tenant of a meeting of
its creditors or any significant class thereof for purposes of effecting a
moratorium upon or extension or composition of its debts; or the failure of
Tenant generally to pay its debts as they mature;

                  (4) If a guarantor of this Lease, if any, or a general partner
or member of Tenant (if Tenant is a partnership, venture or company), becomes a
debtor under any Bankruptcy Proceeding, or becomes subject to receivership or
trusteeship proceedings, whether voluntary or involuntary; unless a substitute
guarantor, acceptable to Landlord in light of the responsibilities of Tenant
under this Lease, is provided to Landlord within 15 days;

                  (5) If Tenant abandons the Premises for 10 consecutive days
with nonpayment of rent, other than as a result of a casualty or condemnation;

                  (6) If Tenant fails to take possession of the Premises and pay
rent within 30 days after it is Substantially Complete;

                  (7) If Tenant fails to perform or breaches any of the other
agreements, terms, covenants or conditions hereof on Tenant's part to be
performed (other than the obligation to pay Rent or any other charges payable
hereunder), and that default continues for a period of 30 days after notice by
Landlord to Tenant; provided, however, that if Tenant cannot reasonably cure the
default within 30 days, Tenant shall not be in default if it commences to cure
the default within that 30 days and diligently pursues it to completion within a
reasonable period of time, not to exceed 60 days.

            B. Remedies of Landlord. If any one or more Event of Default occurs
Landlord shall have the right at Landlord's election, then or at any time
thereafter, in addition to its other rights and remedies under this Lease or any
Laws, to do any one or more of the following:

                  (1) (a) Without demand or notice except as required by Laws,
to enter and retake possession of the Premises or any part of it and expel
Tenant and those claiming through or under Tenant and remove the effects of both
or either, without being guilty of trespass and without prejudice to any
remedies for unpaid of Rent or other breach of this Lease. If Landlord elects to
enter and retake possession pursuant to legal proceedings or pursuant to any
notice provided for by Laws, Landlord may, from time to time, without
terminating this Lease, relet the Premises or any part of it, in Landlord's or
Tenant's name but for the account of Tenant, for such periods (which may be
greater or less than the period which would otherwise have constituted the
balance of the Lease Term) and on such conditions and upon such other terms
(which may include, among other terms, leasing and brokerage fees, concessions
of free rent and alteration and repair of the Premises) as Landlord, in its sole
discretion, may determine, and Landlord shall be entitled to collect all the
rents from the reletting.


                                       17
<PAGE>

Landlord shall in no way be responsible or liable for any failure to relet the
Premises or any part of it, or for any failure to collect any rent due upon
reletting. No such entry or repossession or notice by Landlord shall be
construed as an election on Landlord's part to terminate this Lease, unless
written notice of termination is given to Tenant. Landlord reserves the right
following any such entry and/or reletting to exercise its right to terminate
this Lease by giving Tenant notice, in which event the Lease will terminate as
specified in that notice.

                        (b) If Landlord takes possession of the Premises without
terminating this Lease, Tenant shall pay to Landlord (i) the Rent and other sums
payable under this Lease, less (ii) the net proceeds, if any, of any reletting
of the Premises after deducting all of Landlord's expenses incurred in
connection with the reletting, including all repossession costs, leasing and
brokerage fees, concessions, attorneys' fees, expenses of employees, alteration
and repair costs ("Reletting Expenses"). If, in connection with any reletting,
the new lease term extends beyond the Lease Term or the premises covered thereby
include other premises not part of the Premises, a fair apportionment of the
Rent received from the reletting and the Reletting Expenses will be made in
determining the net proceeds received from the reletting. In determining the net
proceeds, any rent concessions will be apportioned over the term of the new
lease. Tenant shall pay the amount due under this Paragraph to Landlord monthly
on the days on which Rent is due under this Lease.

                  (2) To give Tenant notice of termination of this Lease on the
date specified in that notice, and on that date Tenant's right to possession of
the Premises shall cease and this Lease shall terminate except as to Tenant's
liability as provided below. In the event this Lease is terminated pursuant to
the provisions of this subparagraph), Tenant shall remain liable to Landlord for
damages in an amount equal to the Rent and other amounts which would have been
owing by Tenant for the balance of the Lease Term had this Lease not terminated,
less the net proceeds, if any, from reletting of the Premises by Landlord
subsequent to termination, after deducting the Reletting Expenses. Landlord
shall be entitled to collect such damages from Tenant monthly on the days on
which Rent would have been payable if this Lease had not been terminated.
Alternatively, if this Lease is terminated, Landlord at its option may recover
immediately from Tenant as damages for loss of the bargain and not as a penalty
an amount equal to the worth at the time of termination of the excess, if any,
of the Rent payable under this Lease for the balance of the Lease Term over the
then Reasonable Rental Value of the Premises for the same period, reduced to
present value at a discount rate of 6%. "Reasonable Rental Value" shall be the
amount of rent Landlord can obtain for the remaining balance of the Lease Term,
taking into account a reasonable period for reletting, after deducting all
estimated Reletting Expenses.

                  (3) Advance such monies, and take such other action, for
Tenant's account as reasonably may be required to perform Tenant's obligation or
to mitigate any default or Event of Default, but no such advance or action shall
cure the default or Event of Default. Tenant agrees to reimburse Landlord for
any such advances, as Additional Rent, upon demand from Landlord. Any such
advance, and any cost or expense so incurred, shall bear interest at the rate of
1-1/2% per month, compounded monthly, until paid by Tenant.

                  (4) Suits for the recovery of Rent and damages may be brought
by Landlord, from time to time, at Landlord's election, and nothing herein shall
be deemed to require Landlord to wait until each installment is due or until the
expiration of the Lease Term. Each right and remedy provided for in this Lease
shall be cumulative and in addition to every other right or remedy provided for
in this Lease or now or hereafter existing at law or equity or otherwise,
including, but not limited to, suits for injunctive relief and specific
performance. The exercise or beginning of the exercise by Landlord of any one or
more rights or remedies shall not preclude the simultaneous or later exercise by
Landlord of other rights or remedies. All costs incurred by Landlord in
connection with collecting Rent or other amounts and damages owing by Tenant or
to enforce any provision of this Lease, shall also be recoverable by Landlord
from Tenant.

                  (5) No failure by Landlord to insist upon the strict
performance of any agreement, term, covenant or condition hereof or to exercise
any right or remedy, and no acceptance


                                       18
<PAGE>

of full or partial Rent during the continuance of any such breach shall
constitute a waiver of any such breach or agreement, term, covenant, or
condition, except by written instrument executed by Landlord or relieve Tenant
from the obligation to make the full payment as and when due. No waiver shall
affect or alter this Lease, and each and every agreement, term, covenant, and
condition hereof shall continue in full force and effect with respect to any
other then existing or subsequent breach.

                  (6) Nothing contained in this Lease shall limit or prejudice
the right of Landlord to obtain as liquidated damages in any bankruptcy or
similar proceeding the maximum amount allowed by Law at the time such damages
are proven, whether or not the amount is greater, equal to, or less than the
amounts recoverable, either as damages or Rent, referred to in any of the
preceding provisions of this Paragraph.

            C. Late Charges and Interest.

                  (1) Rent or other amounts owed by Tenant which are not
received by Landlord by the 5th day after the date they are due shall be subject
to a late charge of 5% of the amount due. Additionally, if Rent is not received
by Landlord within 15 days after it is due (or after notice of default, if
notice is required), the amount due shall be subject to an additional 5% late
charge. Rent and all other monetary obligations under this Lease not received by
Landlord when due shall also bear interest at the rate of 1.5% per month,
compounded monthly, from the date due until fully received by Landlord. Tenant
acknowledges that late payments will cause Landlord to incur costs not
contemplated by this Lease, the exact amount of which would be impossible or
extremely difficult to ascertain. Those costs include processing and accounting
charges, interest and late charges imposed by Mortgagees, and other general and
administrative expenses. Tenant agrees that the late charges and interest
contemplated by this Paragraph represent a fair and reasonable estimate of the
costs which Landlord will incur as a result of any such late payments by Tenant.
Acceptance of late charges and interest by Landlord shall not constitute a
waiver of Tenant's default with respect to any overdue amount, or prevent
Landlord from exercising any other rights or remedies under this Lease.

            D. Mitigation. Notwithstanding anything to the contrary contained
elsewhere in this Lease, if Landlord terminates Tenant's right of possession
without terminating this Lease, Landlord shall use reasonable efforts to relet
the Premises so as to mitigate its damages pursuant to this Paragraph, provided,
however, that so long as Landlord uses such reasonable efforts Landlord shall in
no way be responsible or liable for any failure to relet the Premises, or any
part of it, or for any failure to collect any Rent due upon any such reletting;
and Landlord shall not be required to spend its own funds, to give priority (or
even equal opportunity) to the Premises over other rental space owned by
Landlord or its affiliates or to compromise in any way the terms, uses or credit
worthiness of a tenant upon or to which it would customarily lease space such as
the Premises; and Landlord shall be entitled, in its sole discretion, to seek a
single tenant for the entire Premises, even though it may take a substantially
longer period to obtain such a tenant and its efforts may be unsuccessful; and
this requirement shall not affect in any way Tenant's obligation to obtain
Landlord's consent as under Paragraph 14.

            E. No Waiver. No payments of Rent or money by Tenant to Landlord
after notice of termination or after termination of this Lease, in any manner,
shall reinstate, continue, or extend the term of this Lease or affect any notice
given to Tenant prior to the payment, it being agreed that after the service of
notice of termination or the commencement of a suit or other final judgment
granting Landlord possession of the Premises, Landlord may receive and collect
any sums of Rent due or an other sums of money, whether as Rent or otherwise,
and exercise Landlord's rights and remedies hereunder, and shall not waive any
default or notice or in any manner affect any pending suit or judgment.

            F. Landlord's Lien. [Intentionally Omitted]


                                       19
<PAGE>

      21. SUBORDINATION AND ATTORNMENT.

            A. General. This Lease, and all rights of Tenant under it, at
Landlord's option shall be subordinate to any ground leases, deeds of trust,
mortgages and security agreements, including leasehold mortgages and building
loan agreements, now or hereafter placed upon the Building or the Building
Complex (including all advances made thereunder), and to all amendments,
renewals, replacements and extensions thereof (collectively, "Mortgage"), but
only if and when any Lessor or Mortgagee (as defined below) executes and
delivers to Tenant a non-disturbance and attornment agreement reasonably
acceptable to Landlord, Tenant and the Lessor or Mortgagee, under which, among
other provisions which may be included (1) Tenant agrees to recognize and attorn
to the Lessor or Mortgagee if it becomes the Landlord under this Lease, and (2)
the Lessor or Mortgagee (on behalf of itself and its successors and assigns in
interest) agrees to recognize Tenant's rights under this Lease as long as Tenant
is not in default under this Lease beyond applicable grace and cure periods,
notwithstanding defaults under any such ground lease or Mortgage or foreclosure,
receivership or sale thereunder. If any holder of a Mortgage ("Mortgagee") or
the lessor of any ground lease ("Lessor") elects to have this Lease made
superior to the lien of its Mortgage and gives notice to Tenant, this Lease will
be deemed prior to that Mortgage, whether this Lease is dated prior or
subsequent to the date of that Mortgage. In confirmation of this non-disturbance
and attornment, subordination or superior position, as the case may be, Tenant
shall promptly execute and deliver to Landlord (or such other party so
designated by Landlord) at Tenant's own cost and expense, within 10 days after
request from Landlord any instruments as may be reasonably required for this
purpose by Mortgagee or Lessor, in recordable form if requested. If Tenant fails
to do so within that 10-day period, Tenant shall be in default under this Lease,
and Tenant hereby irrevocably grants to Landlord a power of attorney coupled
with an interest to act as Tenant's attorney-in-fact for the purposes of
executing whatever documents are necessary to evidence such subordination or
superior position. Tenant agrees to attorns to all successor owners of the
Building, whether such ownership is acquired by sale, foreclosure of a Mortgage,
or otherwise.

            B. Lease Modifications. If, in connection with the procurement,
continuation or renewal of any financing for the Building or the Building
Complex, the Mortgagee requests reasonable modifications of this Lease, Tenant
will not unreasonably withhold its consent, provided the modifications does not
adversely affect any rights of Tenant, or increase the economic costs or
obligations of Tenant under this Lease or decrease the obligations of Landlord
under this Lease.

      22. SURRENDER AND HOLDING OVER.

            A. Surrender. Upon the expiration or termination of this Lease or
termination of Tenant's right of possession, Tenant shall promptly surrender the
Premises to Landlord broom clean, in good order and condition, ordinary wear and
tear and loss by fire or other insured casualty excepted (except as otherwise
provided in Paragraphs 16 and 17), and Tenant shall remove Tenant's Property and
other property as required under Paragraph 11 and the Alterations and other
property as required under Paragraph 11. If Tenant fails to vacate the Premises
on a timely basis as required, Tenant shall be liable to Landlord for all costs
reasonably incurred or which could not have been reasonably avoided by Landlord
provided, however, Tenant's liability shall not exceed in the aggregate
$400,000, incurred by Landlord as a result of that failure, including, but not
limited to, any amounts required to be paid to third parties who were to have
occupied the Premises.

            B. Property Not Removed. All Tenant's Property not removed from the
Premises upon the termination of this Lease or of Tenant's right of possession
for any cause whatsoever shall conclusively be deemed to have been abandoned and
may be appropriated, sold, stored, destroyed, or otherwise disposed of by
Landlord without notice to Tenant or any other person and without obligation to
account therefor, Tenant shall pay Landlord all expenses incurred in so doing.

            C. Holding Over, If, after the termination of this Lease or of
Tenant's right of possession, Tenant remains in possession of the Premises and
continues to pay Rent, and Landlord consents to the possession and accepts the
Rent, without any written agreement, the holding over shall


                                       20
<PAGE>

be deemed a tenancy from month-to-month, under all the provisions of this Lease,
but at a monthly Rent equivalent to 150% of the monthly installments of Rent
paid by Tenant immediately prior to the termination or the current market rental
rate for the Premises, whichever is greater. If, after the termination of this
Lease or of Tenant's right of possession, Tenant remains in possession without
Landlord's consent, Landlord will suffer damages, the amount of which will be
difficult to determine; therefore, Tenant shall pay to Landlord as liquidated
damages an amount equal to 200% of the Rent calculated on a per diem basis,
applicable under the Lease in the month immediately prior to the termination.
All such Rent shall be payable in advance on the same day of each month. The
month-to-month tenancy may be terminated by either party upon 10 days' notice
prior to the end of any such monthly period. Nothing contained herein shall be
construed as obligating Landlord to accept any Rent tendered by Tenant after any
such termination or as obligating Landlord to consent to any holding over, or as
relieving Tenant of its liability under this Lease.

      23. LANDLORD DEFAULT. In the event of any noncompliance with the terms and
conditions of this Lease by Landlord, Tenant shall, before exercising any right
or remedy available to it at law, in equity or hereunder, give Landlord written
notice of such noncompliance. If prior to its giving such notice, Tenant has
been notified in writing (by way of notice of Assignment of Rents and Leases by
execution of a subordination agreement, or by notice delivered in accordance
with the provisions of Paragraph 24 hereof) of the address of a Mortgagee which
has furnished any of the financing referred to in Paragraph 21 hereof,
concurrently with giving the aforesaid notice to Landlord, Tenant shall, by
registered mail, transmit a copy thereof to such Mortgagee. For the 30 days
following the giving of the notice(s) required by the foregoing portion of this
Section 22 (or such longer period of time as may be reasonably required to cure
a matter which, due to its nature, cannot be reasonably rectified within 30
days), Landlord shall have the right to cure the noncompliance involved. If
Landlord has failed to effect such cure within such period, any such Mortgagee
shall have 30 days within which to cure the same, or, if such default cannot be
cured within that period, such additional time as may be reasonably necessary to
cure such default, if within such period, said Mortgagee has commenced and
diligently pursues the actions or remedies to completion; provided, however,
that any such cure must be completed within 160 days following Landlord's cure
period. Notwithstanding the foregoing, in case of a bona fide emergency and
which results in a substantial portion of the Premises being untenantable not
arising as a result of the Non-Abatement Conditions, as hereinafter defined, and
as a result, Tenant has not occupied such portion of the Premises for at least 7
consecutive days, (i) Tenant shall not be required to give written notice, but
may, instead, give oral telephone notice to Landlord (so long as such oral
notice is promptly followed by written notice, which may be by means of
facsimile transmission), and (ii) neither Landlord nor such Mortgagee shall be
entitled to such 30-day period to cure any such noncompliance and, instead,
Landlord and such Mortgagee shall have such shorter time as is reasonably
necessary to cure such noncompliance in light of the nature of the emergency and
all surrounding circumstances. Upon Landlord's (and Mortgagee's, if applicable)
failure to cure any failure of its performance of any of its covenants or
obligations as set forth in this Lease beyond the cure period set forth herein,
Tenant, at its option, but without obligation, may perform such acts and pay
such amounts as are reasonably necessary to cure such default by Landlord, and
Landlord shall reimburse Tenant for the out-of-pocket costs reasonably incurred
in connection therewith within 30 days following receipt of Tenant's written
request with accompanying paid invoices evidencing such costs. If such amounts
are not paid by Landlord within said 30 days, Tenant shall have the right to
offset such amounts against the Base Rent due under this Lease. "Non-Abatement
Conditions" shall mean if the emergency condition arises as a result of, (1) the
failure of Tenant to comply with the requirements of this Lease for occupancy
and use, (2) as to HVAC, the Premises is not being utilized in accordance with
the Premises' HVAC and electrical systems and (3) Tenant's installation or use
of the Fiber Optic Cable and/or UPS Installation, as hereinafter defined.
Further, notwithstanding the foregoing to the contrary, if the reason any such
emergency arises is due to force majeure events, including, but not limited to,
a (a) failure to furnish or delay in furnishing any such utilities or services
when such failure or delay is caused by acts of God or the elements, labor
disturbances of any character, Tenant's negligence or wilful misconduct, or
other conditions the remedy for which is beyond the control of Landlord, and/or
(b) the limitation, curtailment, rationing or restriction on use of water or
electricity, gas or any other form of energy or any other service or utility
whatsoever serving the Premises or the Buildings Complex by utility providers or
as a result of acts of governmental authorities


                                       21
<PAGE>

including under Applicable Laws, the foregoing offset right shall not be
available to the Tenant. Finally, provided the Tenant has complied with the
notice to Landlord and Mortgagee (and afforded the cure opportunities) pursuant
to the terms of the first four sentences of this Paragraph, and has not elected
to avail itself of the offset provisions of this Paragraph as Tenant's remedy,
the Tenant shall be entitled to equitable relief and actual damages, but not
consequential or punitive damages, for Landlord's breach of Landlord's
obligations hereunder.

      24. NOTICE. All notices, demands or statements required or permitted to be
given to Landlord shall be in writing and shall be deemed duly served when
deposited in the United States mail, postage prepaid, certified or registered,
return receipt requested, addressed to Landlord at Landlord's address shown on
the Basic Lease Term Sheet or at the most recent address of which Landlord has
notified Tenant in writing. All notices, demands or statements required or
permitted to be given to Tenant shall be in writing and shall be deemed duly
served when delivered, or when deposited in the United States mail, postage
prepaid, certified or registered, return receipt requested, addressed to Tenant
at the address for notices shown on the Basic Lease term Sheet with a copy to
Foley, Hoag & Elliot LLP, One Post Office Square, Boston, MA 02019, Attn: John
D. Patterson, Jr. Esq. Either party shall have the right to designate in
writing, served as above provided, a different address to which notice is to be
delivered. This Paragraph shall not prohibit notice from being given as provided
in Rule 4 of Colorado Rules of Civil Procedure, as amended from time to time.

      25. RULES AND REGULATIONS. The rules and regulations attached as Exhibit D
are deemed a part of this Lease, and Tenant agrees that Tenant and its
employees, agents or any others permitted by Tenant to occupy or enter the
Premises shall at all times abide by those rules and regulations. Tenant agrees
that Landlord may reasonably change the rules and regulations for the Premises
and the Building Complex from time to time (including the addition of rules and
regulations regarding parking), and Tenant agrees to abide by them upon receipt
of notice of the change.

      26. PARKING. Tenant shall have the right to use only the number of parking
spaces indicated on the Basic Lease Term Sheet and any use of additional parking
spaces by Tenant may be deemed by Landlord as a default under this Lease. All
vehicles parked in the parking spaces are at the sole risk of Tenant, Tenant's
agents and invitees and Landlord shall have no liability for loss or damage.

      27. RIGHT TO RELOCATE TENANT. [INTENTIONALLY OMITTED]

      28. MISCELLANEOUS.

            A. Limitation of Landlord's Liability. The term "Landlord" as used
in this Lease, so far as covenants or obligations on the part of Landlord are
concerned, shall mean and include only the owner or owners of the Building at
the time in question and, in the event of any transfer or transfers of the title
thereto, Landlord herein named (and in the case of any subsequent transfers or
conveyances, the then grantor) shall be automatically released, from and after
the date of the transfer or conveyance, of all liability as respects the
performance of any covenants or obligations on the part of Landlord thereafter
to be performed, provided that the Security Deposit then held by Landlord or the
then grantor at the time of the transfer shall be delivered to or credited to
the purchase price paid by the grantee and the grantee assumes all of Landlord's
(or the then grantor's) obligations under this Lease. Notwithstanding anything
to the contrary contained herein, Landlord's liability under this Lease shall be
limited to Landlord's interest in the Building Complex, and Tenant shall not and
cannot seek any recovery or deficiency against any other assets or against any
partners, lenders, officers, directors, or employees of Landlord or against the
Building Manager.

            B. No Merger. The termination of this Lease shall not be a merger,
and such termination shall, at the option of Landlord, either terminate all
subleases and subtenancies or operate as an assignment to Landlord of any or all
such subleases or subtenancies.

            C. Landlord's Use of Common Areas. Tenant agrees that Landlord has
the right to use the Common Areas for the general benefit of the Building
Complex, including for the purposes


                                       22
<PAGE>

of completing or making repairs or alterations in any portion of the Building.
Landlord may use the Building Complex, the Common Areas and one or more of the
street entrances to the Building Complex as may be necessary in Landlord's
judgment to complete any such work or for other purposes in connection with
Landlord's management or operation of the Building Complex..

            D. Covenants are Independent. This Lease shall be construed as
though the covenants between Landlord and Tenant are independent and not
dependent, and subject to Paragraph 23, Tenant shall not be entitled to any set
off of the Rent or other amounts owing hereunder against Landlord if Landlord
fails to perform its obligations

            E. Severability. If any provision of this Lease is held by a court
of competent jurisdiction to be illegal, invalid, or unenforceable under any
Laws, it is the intention of the parties that the remainder of this Lease shall
not be affected and that the illegal, invalid, or unenforceable provision be
replaced by a provision (or construed to be) as similar in terms as possible and
be legal, valid, and enforceable.

            F. Captions and Terms. The caption of each Paragraph is added as a
matter of convenience only and shall have no effect on the construction of any
provision or provisions of this Lease. The words "include" and "including" when
used in this Lease are intended in their illustrative sense, not as a
limitation, and the terms that follow such words are illustrative and not
exclusive. References to "provisions" of this Lease refers to all of the
provisions, terms, conditions, covenants and agreements in this Lease. The words
"shall" and "will" have the same meaning.

            G. Binding Effect; Governing Law. Subject to Paragraphs 14 and 29A,
this Lease shall inure to the benefit of, and be binding upon, Landlord and
Tenant and their respective heirs, administrators, successors and assigns. This
Lease is subject to and shall be construed in accordance with Colorado law.

            H. Tenant's Authority. Tenant and the party executing this Lease on
behalf of Tenant represent to Landlord that they are authorized to do so by
requisite action of Tenant and that this Lease is binding on Tenant, and agree,
upon request, to deliver to Landlord a resolution or similar document to that
effect.

            I. Joint and Several. If there are more than one entity or person
which are the Tenant under this Lease, the obligations imposed upon Tenant under
this Lease shall be joint and several.

            J. Acts Binding Landlord. No act or thing done by Landlord or
Landlord's agents during the term, including any agreement to accept the
surrender of the Premises or to amend or modify this Lease, shall be binding on
Landlord, unless in writing and signed by a person authorized to bind Landlord.
The delivery of keys to Landlord, or Landlord's agents, employees, or officers
shall not operate as a termination of this Lease or a surrender of the Premises.
No payment by Tenant or receipt by Landlord of a lesser amount than the full
monthly Rent and all other amounts owing, as herein stipulated, shall be deemed
to be other than on account of the earliest due Rent or other amounts, nor shall
any endorsement or statement on any check or any letter accompanying any check
or payment as Rent be deemed an accord and satisfaction. Landlord may accept any
such check or payment without prejudice to Landlord's right to recover the
balance owed or to pursue any other remedy available to Landlord.

            K. Change in Light or View. Tenant agrees that no diminution of
light, air, or view by any structure that may hereafter be erected (whether or
not by Landlord) shall entitle Tenant to any reduction of Rent or other charges
under this Lease, result in any liability of Landlord to Tenant, or in any way
affect this Lease or Tenant's obligations under it.

            L. No Other Agreements; Amendments. Tenant acknowledges and agrees
that it has not relied upon any statements, representations, agreements, or
warranties by Landlord, its agents


                                       23
<PAGE>

or employees, except those expressed in this Lease and that no amendment or
modification of this Lease shall be valid or binding unless in writing and
executed by the parties hereto in the same manner as the execution of this
Lease, and that this Lease incorporates all prior discussions and agreements.

            M. Brokers. Tenant represents and warrants to Landlord that no
broker or agent negotiated or was instrumental in the negotiation or
consummation of this Lease, except Landlord s Broker and any Tenant's Broker
specified in the Basic Lease Term Sheet. Landlord shall be responsible for
payment of any commission to Landlord's Broker and/or Tenant's Broker. Tenant
agrees to indemnify and hold Landlord harmless from and against any loss,
expense, cost or liability incurred by Landlord as a result of a claim by any
other broker or finder, whether or not meritorious, claiming through Tenant.
Tenant acknowledges Landlord is not liable for any representations by Landlord's
Broker or Tenant's Broker regarding the Premises, the Building, the Building
Complex or this Lease.

            N. Recordation. Tenant shall not record or permit to be recorded
this Lease or any memorandum of it; and any such recording shall be an Event of
Default.

            O. Execution Required. Submission of this Lease or any letter
regarding it for examination or signature by Tenant shall not grant to Tenant an
option or right to lease the Premises; and this Lease shall not be effective as
a lease or otherwise binding on either party until execution and delivery by
both Landlord and Tenant.

            P. Attorney's Fees. If either party brings an action to enforce any
provision of this Lease, the prevailing party shall be entitled to recover its
reasonable attorney's fees, as determined by the court.

            Q. Time of Essence: Effective Dates. Time is of the essence herein.
This Lease shall become effective only upon execution by Landlord and delivery
of a fully-executed copy of this Lease to Tenant.

      29. OPTION TO EXTEND. As additional consideration for the covenants of
Tenant hereunder, Landlord hereby grants Tenant an option (the "Option") to
extend the term of the Lease for one (1) term of five (5) years (the "Option
Term"). The Option shall apply to all space contained in the Premises at the
time and shall be on the following terms and conditions:

      A. Exercise of Option. Written notice of Tenant's exercising an Option
("Notice") shall be given to Landlord no earlier than 12 months and no less than
9 months prior to the expiration of the Primary Lease Term and, upon the giving
of such Notice, this Lease and the Lease Term shall be extended with the same
force and effect as if the Option Term had originally been included in the Lease
Term and the Expiration Date shall thereupon be deemed to be the last day of the
Option Term. Tenant's right to exercise the Option shall be conditioned on there
being no uncured Event of Default under the Lease at the time of exercise of the
Option or at the time of the commencement of the Option Term.

      B. Rent Determination. The Option granted hereunder shall be upon the
terms and conditions contained in the Lease except (i) rights of first offer or
abilities to request expansion space shall not be applicable, (ii) no Landlord's
contributions, tenant allowances or similar concessions shall be applicable,
(iii) no leasing commissions shall be payable by Landlord, (iv) the Rent to be
paid by Tenant to Landlord during the Option shall be the then Market Rate, as
hereinafter defined. Subject to said caveat, Rent for the Option Term shall be
determined as follows:

            1. Within 14 days of Landlord's receipt of the Option Notice,
Landlord shall notify Tenant in writing ("Landlord's Notice") of the proposed
Market Rate, and the resulting Rent, applicable to the Option ("Landlord's Rent
Rate"). Tenant shall, within 14 days following receipt of Landlord's Notice,
notify Landlord in writing of the acceptance or rejection of the Landlord's Rent
Rate set forth therein. If Tenant fails to respond to Landlord's Notice within
such 14-day period, Tenant shall be deemed to have accepted Landlord's Rent
Rate. If Tenant rejects Landlord's Rent Rate, Tenant's


                                       24
<PAGE>

rejection notice shall state Tenant's estimate of the Market Rate, and the
resulting Rent, applicable to the Option ("Tenant's Rent Rate"). Landlord shall,
within 14 days following receipt of notice of Tenant's Rent Rate, notify Tenant
of its acceptance of the Tenant's Rent Rate. If Landlord fails to respond within
such 14-day period, Landlord shall be deemed to have rejected Tenant's Rent
Rate. Landlord and Tenant shall act in good faith in estimating and proposing
their respective determinations of the Market Rate.

            2. If Landlord rejects Tenant's Rent Rate, the parties shall
thereafter attempt to negotiate the Rent in good faith. If, however, the parties
have not agreed on the Rent within 40 days after the date of the Option Notice,
the Rent for the renewal term in question shall be determined as set forth
below:

                  a. Within 60 days after delivery by Tenant of the Option
Notice, Landlord and Tenant shall each appoint an Appraiser, as hereinafter
defined. The two Appraisers shall meet promptly and attempt to determine the
Market Rate for the renewal term in question. The determination made by the two
Appraisers, if they agree, shall be the Market Rate. If the amounts determined
by the two Appraisers vary by less than 5%, then the average of the two values
shall be the Market Rate.

                  b. If the Market Rate is not established pursuant to
sub-paragraph (a) within 10 days following their appointment, the two Appraisers
shall immediately select a third Appraiser. If they are unable to agree on a
third Appraiser within 5 days, then they shall each select the names of two
willing persons qualified to be Appraisers hereunder and from the four persons
so named, one name shall be drawn by lot by a representative of Tenant in the
presence of a representative of Landlord, and the person whose name is so drawn
shall be the third Appraiser. If either of the first two Appraisers fails to
select the names of two willing, qualified Appraisers so that a third Appraiser
can be selected by lot, as aforesaid, the third Appraiser shall be selected by
lot from the two Appraisers which were selected by the other Appraiser for the
drawing. The three Appraisers so selected shall confer and immediately proceed
to determine the Market Rate for the renewal term in question. If the three
Appraisers fail to agree on such Market Rate within 10 days after the selection
of the third Appraiser, the average of the two determinations of Market Rate
which are closest to each other shall be the Market Rate for the renewal term in
question.

                  c. The Appraisers selected hereunder shall deliver a signed
written report of their appraisal, or the average of the two closer appraisals,
as the case may be, to Tenant and Landlord. The fee of the Appraiser initially
selected by Tenant shall be paid by Tenant, the fee of the Appraiser initially
selected by Landlord shall be paid by Landlord, and the fee of any third
Appraiser and any expenses reasonably incident to the appraisal (except
attorneys' fees, which shall be borne by the party incurring the same) shall be
shared equally by Tenant and Landlord. Any vacancy in the office of the
Appraiser appointed by Tenant shall be filled by Tenant, any vacancy in the
office of the Appraiser appointed by Landlord shall be filled by Landlord, and
any vacancy in the office of the third Appraiser shall be filled by the first
two Appraisers in the manner specified above for the selection of a third
Appraiser.

                  d. If appraisal proceedings are initiated as provided above in
order to determine the Market Rate which is applicable to the term of the
Option, the decision and award of the Appraisers as to such Market Rate shall be
final, conclusive, and binding on the parties, absent settlement by agreement of
the parties prior to the rendering by the Appraisers of any such decision and
award and, further, as provided above, the Rent will be the Market Rate for the
applicable renewal term.

                  e. If Rent is not finally determined prior to the commencement
of the term of the Option, Tenant shall pay Rent in the amount of the Rent
theretofore in effect under this Lease until the final determination of the Rent
for the renewal term in question occurs as provided above. If the final
determination of such Rent is different from the amount paid by Tenant, Tenant
shall promptly pay to Landlord any deficiency in Rent or Landlord shall promptly
pay to Tenant any overpayment of Rent from the commencement of the term of the
Option until such final determination. If appraisal


                                       25
<PAGE>

proceedings are initiated, as provided above, neither Landlord nor Tenant shall
disclose its initial proposal for Market Rate to any of the Appraisers.

      C. Appraiser Defined. "Appraiser," used herein, shall mean a person (A)
who is impartial, (B) who has at least ten years' experience as a real estate
broker in the office building leasing market for the Northwest/Interlocken
Denver, Colorado area, (C) who is a senior employee of a nationally or
regionally recognized brokerage firm who has not acted as the primary
representative on such broker's firm's account for either Landlord or Tenant in
the previous three years, and (D) who is a Colorado licensed real estate broker
in good standing and is a member of the Society of Industrial and Office
Realtors, or a successor or similar organization of recognized national
standing.

      D. Market Rate Defined. "Market Rate" shall mean the annual rental rates
then being charged in the Building and in the Northwest/Interlocken Denver,
Colorado area for space comparable to the space for which the Market Rate is
being determined, taking into consideration (i) use, location and floor level
within the applicable building, (ii) the location, quality and age of the
building, (iii) the definition of rentable area or net rentable area, as the
case may be, with respect to which such rental rates are computed, (iv)
leasehold improvements allowances provided, but assume the space has been
previously built out and the leasing of the space is on an "as is" basis, (v)
rental concessions offered with respect to such other space (such as abatements,
lease assumptions or takeovers and moving expenses), (vi) the date the
particular rate under consideration became effective, (vii) the term of the
lease under consideration, (viii) the fact that no brokers' commissions will be
payable by Landlord in connection with the Option, (ix) the extent of services
provided thereunder, (x) applicable distinctions between "gross" leases and
"net" leases, (xi) the credit rating or worthiness of the Tenant under this
Lease, (xii) any other adjustments (including by way of indexes) to rental,
(xiii) availability, nature and quality of parking, and (xiv) any other relevant
term or condition in making such evaluation.

      E. Expiration of Option. After failure to exercise the Option above
described, there shall be no further rights on the part of Tenant to extend the
term of the Lease.

      30. RIGHT OF FIRST OFFER. Subject to the renewal options, expansion
options, and rights of first refusal or offer granted in written leases entered
into with the initial tenants first occupying space in the Building, and whether
such initial tenant leases are entered into before or after the date of this
Lease, if during the Primary Lease Term hereunder, Landlord shall receive a
written bona fide offer ("Offer"), satisfactory to Landlord in its sole
discretion, to lease approximately 17,218 rentable square feet adjacent to the
Premises in the Building as depicted on Exhibit A-1 attached hereto (the "Offer
Space"), Landlord agrees to offer to Tenant, by notice ("Offer Notice"), the
one-time right to lease the Offer Space upon the same terms and conditions set
forth in the Offer and, at Tenant's election, Tenant may elect to lease such
same on the same terms and conditions set forth in the Offer, as adjusted to
reflect the number of months remaining in the initial Term. It is expressly
understood and agreed that if the Offer is for more than the 17,218 rentable
square feet depicted on Exhibit A-1 the term Offer Space shall include such
additional square footage and Tenant's rights hereunder shall only be available
to Tenant for the entire Offer Space as set forth in the Offer.

      A. Exercise. Provided this Lease shall then be in full force and effect
and Tenant shall not be in default hereunder beyond any applicable notice and
grace period, Tenant may exercise its right to lease the Offer Space by written
notice to Landlord within 5 days after the date of the Offer Notice, the time of
the giving of such notice to be of the essence of this Paragraph, in which event
Landlord and Tenant shall enter into a amendment of this Lease, reasonably
acceptable to Landlord and Tenant, to incorporate the terms and conditions set
forth in the Offer. In the event that Tenant fails to accept the offer contained
in the Offer Notice within such 5 day period or fails to execute an Amendment
modifying this Lease to incorporate the terms and conditions contained in the
Offer within 5 days after such Amendment has been delivered to Tenant, Tenant
shall be deemed to have waived its rights under this Paragraph to lease the
Offer Space, Landlord shall have the absolute right to lease the Offer Space to
any other person or entity on any same terms and conditions, in which case
Tenant shall have no further rights with respect to the Offer Space. If Landlord
shall wish to lease the Offer Space on terms and conditions different from those
contained in the Offer, Landlord shall give Tenant a new Offer


                                       26
<PAGE>

Notice, and Tenant shall have the further right to accept the new Offer pursuant
to the terms of this section. Notwithstanding Tenant's acceptance of the Offer
pursuant to the terms of this Paragraph, Landlord shall not be obligated to
deliver possession of the Offer Space to Tenant if, prior to delivery of
possession of the Offer Space, Tenant shall be in Default hereunder beyond any
applicable notice and grace period, in which event the rights of Tenant
hereunder shall terminate and be of no further force or effect.

      B. NO DEFAULT. The option herein granted shall continue only so long as
there have been no uncured Defaults hereunder by Tenant and only so long as
there are at least 36 months remaining on the Primary Lease Term as of the
Offer Space Commencement Date. In the event of an assignment of the Lease or
a subletting (other than an assignment to or subletting of the entire
Premises by a Related Corporation as defined in Paragraph 14.D) or vacation
of more than 25% of the Premises measured at the time of Tenant's exercise of
the Option (other than an assignment to or subletting of the entire Premises
by a Related Corporation), Tenant's rights under this Section shall be of no
force or effect. Further, this right granted in this Section is personal to
Tenant, is not assignable (other than to a Related Corporation assignee) and
may not be exercised by any sublessee or assignee of Tenant (other than to a
Related Corporation assignee or sublessee of the entire Premises), regardless
of whether the sublessee or assignee has been approved by Landlord.

      31. SIGNAGE. Landlord shall provide Tenant, at Landlord's sole cost and
expense, Tenant's prorata share of the existing monument signage located in
the front of the Building for placement of Tenant's name. In addition,
Tenant, at Tenant's sole cost and expense, shall be permitted to install
signage on the glass at the entry to the Premises. All signage is subject to
Landlord's prior consent and approval, not to be unreasonably withheld, and
further must comply with Interlocken's sign code and any other governing
jurisdiction's requirements.

      32. FUEL TANK/UNINTERRUPTED POWER SOURCE. Tenant has previously
installed on Tenant's facility located at 320 Interlocken ("Adjacent
Premises") a supplemental electrical power generator and/or uninterrupted
power source (the "Generator") with an above ground fuel tank integrated into
the Generator ("Tank") to provide emergency additional electrical capacity to
the Adjacent Premises. Hereinafter the Generator and Tank are referred to as
the UPS. Tenant may connect the Premises subject to compliance with the
following provisions:

            A. The UPS will remain installed on the Adjacent Premises. The
Tenant will install all lines, meters, electrical boxes and other equipment
reasonably necessary to connect the Premises to the UPS (collectively, "UPS
Installation") at a location on the Property specified by Landlord; Landlord
shall specify the final location following Landlord's final approval of the UPS
Installation plans and specifications and proof of Tenant's compliance with all
necessary governmental and regulatory approval in accordance with the Work
Letter attached as Exhibit C. Notwithstanding the foregoing, Tenant's right to
install the UPS Installation shall be subject to Landlord's reasonable approval
of the manner in which the UPS Installation is installed, the manner in which
any cables are run to and from the UPS to the Premises and the measures that
will be taken to eliminate any vibrations or sound disturbances from the
operation of the UPS Installation. Tenant shall be solely responsible for
obtaining all necessary governmental and regulatory approvals and all
architectural approvals under the declaration of protective covenants applicable
to the Property as they relate to the UPS and/or UPS Installation. Tenant shall
also be responsible for the cost of installing, operating, maintaining and
removing the UPS Installation. Tenant shall also be responsible for the cost of
all utilities consumed in the operation of the UPS.

            B. Further, Tenant shall be responsible for assuring that the
installation, maintenance, operation and removal of the UPS Installation will in
no way damage the Building or Property. Tenant agrees to be responsible for any
damage caused to the Building or Property in connection with the installation,
maintenance, operation or removal of the UPS Installation and, in accordance
with the terms of Paragraph 14 of the Lease, to indemnify, defend and hold
Landlord harmless from all liabilities, obligations, damages, penalties, claims,
costs, charges and expenses, including, without limitation, reasonable
architects' and attorneys' fees (if and to the extent permitted


                                       27
<PAGE>

by law), which may be imposed upon, incurred by, or asserted against Landlord,
the Building Manager, or Mortgagee in connection with the installation,
maintenance, operation or removal of the UPS, and/or the UPS Installation,
including, without limitation, any environmental and hazardous materials claims.

            C. Tenant shall be responsible for the installation, operation,
cleanliness, maintenance and removal of the UPS Installation and appurtenances,
all of which shall remain the personal property of Tenant, and shall be removed
by Tenant at its own expense at the termination of the Lease; provided, however,
that Tenant shall have the right to leave such equipment on the Property if
approved by Landlord prior to expiration or earlier termination of the Lease.
Tenant shall repair any damage caused by such removal, including the patching of
any holes to match, as closely as possible, the color or material surrounding
the area where the UPS Installation and appurtenances were removed. Such
maintenance and operation shall be performed in a manner to avoid any
unreasonable interference with any other tenants or Landlord. Tenant agrees to
maintain the UPS Installation in good condition and repair.

            D. Subject to the reasonable rules and regulations adopted by
Landlord, Tenant shall have access to the UPS Installation and its surrounding
area for the purpose of installing, repairing, maintaining and removing said UPS
Installation.

            E. Tenant shall only test the UPS before or after normal business
hours and upon prior notice to Landlord. Tenant represents and warrants to
Landlord that it has obtained all necessary governmental, regulatory and
architectural approval for the installation of the UPS on the Adjacent Premises,
including required approvals of the Landlord for the Adjacent Premises for the
UPS and extension of lines therefrom through the adjacent property to the
Building Complex.

                                   "Landlord"

                                   NEW ALLIANCE PROPERTIES, INC.,
                                   a Delaware corporation

                                   By: /s/ Douglas McCormick
                                      ---------------------------------------
                                   As its: Chief Financial Officer
                                          ------------------------------


                                   "Tenant"

                                   LIGHTBRIDGE, INC., a Delaware corporation

                                   By: /s/ Joseph S. Tibbetts, Jr.
                                      ----------------------------------
                                   As its: SR VP & CFO
                                          ------------------------------


                                   Attest:

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


                                       28

<PAGE>

                                    EXHIBIT B

                                LEGAL DESCRIPTION

PARCEL 1:

LOT 2,
BLOCK 1,
REPLAT OF INTERLOCKEN FILING NO. 1,
COUNTY OF BOULDER,
STATE OF COLORADO,


PARCEL 2:

NON-EXCLUSIVE EASEMENTS CREATED BY MASTER DECLARATION OF COVENANTS, CONDITIONS
AND RESTRICTIONS FOR INTERLOCKEN FILED AT RECEPTION NO. 599882 ON JANUARY 20,
1984 AND AMENDED AND RESTATED MASTER DECLARATION OF COVENANTS, CONDITIONS AND
RESTRICTIONS FOR INTERLOCKEN FILED AT RECEPTION NO. 1025034, ON JANUARY 24,
1990, AS AMENDED, COUNTY OF BOULDER, STATE OF COLORADO.


<PAGE>

                                    EXHIBIT C
                                   WORK LETTER

      This is the Work Letter referred to in and specifically made a part of the
Lease to which this Work Letter is annexed, covering the Premises, as more
particularly described in the Lease.

      Landlord and Tenant agree as follows:

1. DEFINED TERMS. The following capitalized terms shall have the meaning set
forth below and, unless provided to the contrary herein, the remaining
capitalized terms set forth herein shall have the meaning set forth in the
Lease:

      Landlord's Representative: John Chambers

      Tenant's Representative:   Michele Ponicsan @ burkettdesign

      Tenant's Architect:        burkettdesign

      Landlord's Contribution:   $80,170.00, plus all costs of installation of
                                 the Meters, as hereinafter defined plus
                                 $4,950.00 towards Premises fire safety system.

2. TENANT IMPROVEMENTS. The "Tenant Improvements" shall mean the interior walls,
partitions, doors, door hardware, wall coverings, wall base, counters, lighting
fixtures, retrofit of existing Premises lighting, electrical and telephone
wiring, removal of all telecommunications cabling throughout the Premises,
cabling for computers, telecommunications and fiber optics cabling, equipment
and conduit necessary to connect the Premises with Tenant's facility located at
320 Interlocken (collectively, "Fiber Optic Cable"), the Water Meter, the UPS
Installation, metering and outlets, ceilings, floor and window coverings, fire
safety system (including electrical fire system panel, additional smoke
detectors, pull stations and horns and lights), Tenant signage, security system,
and other items of general applicability that Tenant desires to be installed in
the interior of the Premises or on the exterior of the Premises or Buildings.
Landlord shall be responsible for installing separate meters to measure the
amount of Tenant's electrical consumption within the Premises (the "Meters")
such that the Premises shall be separately metered and Tenant shall pay directly
to the applicable utility company all utility costs for the Premises and the
HVAC serving the Premises. All costs and expenses associated with such Meters
(such as, but not limited to, installation and preparation of plans and
specifications), shall be paid initially by Landlord. Finally, Tenant
acknowledges that Landlord shall remove from the Premises the Liebert unit
concurrently serving the Premises.

3. DRAWINGS. Subject to the provisions of this Work Letter pertaining to
Landlord's payment of the Landlord's Contribution, Tenant shall engage and pay
for the services of an Architect, which Architect shall be subject to Landlord's
reasonable approval, to prepare a space layout, working drawings and
specifications for all Tenant Improvements, including the location of any Tenant
Improvements located outside of the Premises, including the Fiber Optic Cable,
and UPS Installation. Tenant shall devote such time in consultation with the
Tenant's Architect as shall be necessary to enable the Tenant's Architect to
develop complete and detailed architectural, mechanical and engineering drawings
and specifications for the construction of the Tenant Improvements, showing
thereon all Tenant Improvements, including all materials and specifications
("Drawings"). Tenant hereby acknowledges and agrees that it will endeavor,
through the exercise of its Architect's and other consultants best professional
judgment and skills, to have the Drawings comply with all applicable laws,
including the Americans with Disabilities Act (as currently interpreted), and
other ordinances, orders, rules, regulations and requirements of all
governmental authorities having jurisdiction thereof.


                                      F-1

<PAGE>

4. LANDLORD'S APPROVAL. On or before the applicable Time Limit set forth below,
Tenant shall submit to Landlord complete and final Drawings for the Tenant
Improvements in the form of two sets of Drawings and a computer disk thereof.
The Drawings shall be subject to the approval of Landlord, which approval shall
not be unreasonably withheld. If Landlord should disapprove such Drawings,
Landlord shall specify to Tenant the reasons for its disapproval and Tenant
shall cause the same to be revised to meet the Landlord and Tenant's mutual
reasonable satisfaction and shall resubmit the same to Landlord, as so revised,
on or before the applicable Time Limit set forth in Section 8 below.

5. CONSTRUCTION OF TENANT IMPROVEMENTS. It is understood and agreed by the
parties that, as hereinafter set forth, the Tenant has elected to retain the
General Contractor and arrange for the construction and installation of the
Tenant Improvements itself in a good and workmanlike manner ("Tenant's Work").
All Tenant's Work shall be of a quality and standard equivalent to the standards
for construction set for the Buildings. On or before the Time Limit applicable
set forth below, Tenant shall submit to Landlord the names of the General
Contractor and the electrical, ventilation, plumbing and heating subcontractors
(hereinafter "Major Subcontractors") for Landlord's approval, which approval
shall not be unreasonably withheld. If Landlord shall reject the General
Contractor, any Major Subcontractor Landlord shall advise Tenant of the
reason(s) in writing and, Tenant shall submit another selection to Landlord.
Along with Tenant's notice, Tenant shall notify Landlord of its estimate of the
total costs for the Tenant' Work.

      5.1 Landlord shall be entitled to receive a construction management fee
equal to 3% of all costs, including hard and soft costs, for the Improvements
("Management Fee").

6. TENANT'S CONSTRUCTION OF THE TENANT IMPROVEMENTS. Subject to the provisions
of this Work Letter pertaining to Landlord's payment of Landlord's Contribution
and Landlord's Additional Contribution, Tenant shall promptly pay any and all
costs and expenses in connection with or arising out of the performance of the
Tenant's Work within seven (7) business days of Tenant's receipt of its draw
pursuant to its Draw Request, as hereinafter provided in Section 8 below and
shall furnish to Landlord evidence of such payment upon request. Landlord shall
post and serve notices of non-liability in accordance with C.R.S.
ss.38-22-105(2). In the event any lien is filed against the Buildings, Building
Complex or any portion thereof or against Tenant's leasehold interest therein,
the provisions of the Lease regarding Tenant's removal of mechanic's liens shall
apply.

      6.1 Tenant shall indemnify, defend (with counsel reasonably satisfactory
to Landlord and Tenant) and hold Landlord harmless from and against any and all
suits, claims, actions, loss, cost or expense (including claims for workers'
compensation, attorneys' fees and costs) based on personal injury or property
damage caused in, or contract claims (including, but not limited to claims for
breach of warranty) arising from the construction of the Tenant's Work. Tenant
shall repair or replace (or, at Landlord's election, reimburse Landlord for the
cost of repairing or replacing) any portion of the Buildings or item of
Landlord's equipment or any of Landlord's real or personal property damaged,
lost or destroyed in the construction of the Tenant's Work.

      6.2 The General Contractor employed by Tenant and any subcontractors
thereof shall be (i) duly licensed in the state in which the Premises are
located, and (ii) except as otherwise approved herein or pursuant to Section 6
above, subject to Landlord's prior written approval, which approval shall not be
unreasonably withheld or delayed. On or before fifteen (15) days, prior to the
commencement of any construction activity in the Premises, Tenant and Tenant's
contractors shall obtain and provide Landlord with certificates evidencing
Workers' Compensation, public liability and property damage insurance in amounts
and forms compiling with the insurance requirements of the Lease and with
companies satisfactory to Landlord. If Landlord should disapprove such
insurance, Landlord shall specify to Tenant the reasons for its disapproval
within five (5) business days after delivery of such certificates. Tenant's
agreement with its contractors shall require such contractors to provide daily
clean up of the construction areas to the extent such clean up is necessitated
by the construction of the Tenant Work, and to take reasonable steps to minimize
interference with other tenant's use and occupancy of the Buildings. Nothing
contained herein shall make or constitute Tenant as the agent of


                                      F-2
<PAGE>

Landlord. Tenant and Tenant's contractors shall comply with any other Building
rules, regulations or reasonable requirements that Landlord may impose.

      6.3 Landlord will permit entry of such contractors into the Premises for
the purpose of performing such work or after the date Landlord has approved the
Drawings. Landlord agrees to supply temporary power, material staging area, dock
space, space for Tenant's dumpsters, and access in and out of the Building
during the entire construction period at no cost to Tenant and subject to
reasonable rules established by Landlord. After hours construction activities by
Tenant shall require reimbursement to Landlord for its costs for after hours
supervision. Further, all construction activities shall be conducted so as to
use reasonable efforts to minimize interference with the use and occupancy of
the Building by the tenants thereof. Such entry shall be deemed to be under all
the terms, covenants, provisions and conditions of the Lease, except for the
payment of Rent.

      6.4 All materials, work, installations, equipment and decorations of any
nature whatsoever brought on or installed in the Premises pursuant to the
provisions of this Work Letter before the commencement of the Term or throughout
the Term shall be at Tenant's risk, and neither Landlord nor any party acting on
Landlord's behalf shall be responsible for any damage thereto or loss or
destruction thereof due to any reason or cause whatsoever, excluding by reason
of Landlord or such other party's gross negligence or willful or criminal
misconduct.

7. LANDLORD'S CONTRIBUTIONS. Landlord shall contribute to the costs and expenses
of all consultant costs for the planning and design of Tenant's Work, including
all permits, licenses and construction fees and constructing the Tenant Work in
an amount not to exceed Landlord's Contribution ("Tenant's Costs"). In addition,
if the costs exceed the Landlord's Contribution, Landlord agrees to provide an
additional allowance of up to $5.00 per usable square feet of the Premises (i.e.
$80,170.00) to be amortized over the initial Lease Term with interest thereon at
12% per annum and paid monthly as additional Base Rent in the same manner and
place as monthly Base Rent ("Landlord's Additional Contribution").
Notwithstanding the foregoing, the costs for the design and installation of the
Fiber Optic Cable and UPS Installation shall be Tenant's sole and exclusive
responsibility. If applicable, Tenant agrees to execute an amendment to this
lease reflecting such increase in the Base Rent payable hereunder. Hereinafter
the term "Landlord's Contribution" shall mean the Landlord's Contribution and,
if applicable, the Landlord's Additional Contribution. Provided this Lease is in
full force and effect and Tenant is not in default hereunder beyond any
applicable notice and grace period, Landlord shall pay Landlord's Contribution
to Tenant as follows:

            (1) No more frequently than once every thirty (30) days following
      the Commencement Date, Tenant may request in writing a draw, payable to
      joint check to Tenant and/or Tenant's Contractor and/or any applicable
      subcontractor ("Joint Check") against the Landlord's Contribution which
      request shall include (a) receipted invoices (or such other proof of
      payment as Landlord shall reasonably require) showing payment thereof, (b)
      a written statement from Tenant's Architect or General Contractor that the
      Tenant's Work described on any such invoices has been completed in
      accordance with the Drawings, and (c) all required AIA forms, supporting
      final lien waivers and releases executed by the General Contractor and all
      subcontractors employed in connection with such portion of the Tenant's
      Work (collectively the "Draw Request"). Within ten (10) business days
      following Landlord's receipt and approval of the Draw Request, Landlord
      shall pay the amount of such draw, less ten percent (10%) thereof and less
      the Management Fee applicable to such Draw Amount; and

            (2) After the Tenant's Work is Substantially Complete (as defined in
      Section 10 hereof), Tenant may submit to Landlord a request in writing for
      the balance of Landlord's Contribution which request shall include: (a)
      record "as-built" drawings showing all of Tenant's Work as actually
      constructed, (b) a detailed breakdown of Tenant's final and total
      construction costs, together with receipted invoices showing payment
      thereof in accordance with previous Draw Requests, (c) a certified,
      written statement from Tenant's Architect that all of the Tenant's Work
      has been completed in accordance with the Drawings, (d) all required AIA
      forms, supporting final lien waivers, and releases executed by the
      Architect, General Contractor and


                                      F-3
<PAGE>

      all subcontractors and suppliers in connection with Tenant's Work, and (e)
      a copy of a certificate of occupancy or amended certificate of occupancy
      required with respect to the Premises, together with all licenses,
      certificates, permits and other government authorizations necessary in
      connection with Tenant's Work and the operation of Tenant's business from
      the Premises ("Final Draw Request"). Upon Landlord's receipt and approval
      of the Final Draw Request, Landlord shall pay the balance of Landlord's
      Contribution less the Review Costs, not to exceed $1,000.00, and less the
      Management Fee applicable to such amount, by Joint Check, if requested by
      Tenant. Payment by Landlord shall be made within five (5) business days,
      unless Landlord notifies Tenant, in writing, of its rejection (and the
      reasons therefor) of any or all of the Final Draw Request and, if so, upon
      reasonable satisfaction of such objections, Landlord shall pay any
      remaining sums within five (5) business days. Further, to the extent
      Landlord does not so reject any portion of said Final Draw Request,
      Landlord shall timely pay such acceptable portion of the Final Draw
      Request.

8. TIME LIMITS. The following maximum time limits and periods shall be allowed
for the indicated matters:

                Action                                 Time Limit

o     Tenant notifies Landlord of its     On or before 5 days after the date of
      selection of an Architect.          this Lease.

o     Tenant submits Drawings to          On or before 30 days after the date of
      Landlord for review and             this Lease.
      approval.

o     Landlord notifies Tenant and.       On or before 7 days after the date of
      Tenant's Architect of its           Landlord's receipt of the Drawings.
      approval of the Drawings with
      any required changes in detail.

o     Tenant notifies Landlord of its     On or before 5 days after the date of
      selection of its General            this Lease.
      Contractor and Major
      Subcontractors.

o     Landlord approves/disapproves       On or before 7 days after the date of
      Tenant's General Contractor         Landlord's receipt of Tenant's
      and/or Major Subcontractors.        notification.

o     If applicable, Landlord and         On or before 3 days after the date of
      Tenant mutually approve the         Landlord's receipt of Tenant's revised
      General Contractor and all Major    list.
      Subcontractors.

o     If applicable, Landlord and         On or before 3 days after the date of
      Tenant mutually approve the         Landlord's receipt of revised
      final revised Drawings.             Drawings.

o     Tenant submits Drawings for         On or after the date Tenant and
      building permit.                    Landlord mutually approve the final,
                                          revised Drawings.

o     Tenant commences construction of    After providing copies of the building
      the Tenant's Work.                  permit to Landlord.

      8.1 Except as may be otherwise specifically provided for herein, in all
instances where either Tenant's or Landlord's approval is required, if no
written notice of disapproval is given within the applicable Time Limit, at the
end of such period the applicable party shall be deemed to have given its
approval and the next succeeding time period shall commence. Any delay in any of
the foregoing dates (including any "re-do," continuation or abatement of any
item due to Tenant's or Landlord's disapproval thereof) shall automatically
delay all subsequent deadlines by a like amount of time.


                                      F-4
<PAGE>

9. SUBSTANTIAL COMPLETION. Tenant's Work shall be deemed "Substantially
Complete" when the General Contractor has finished all work called for by the
Drawings and contract documents in a good, workmanlike manner and the Premises
is ready to be used and occupied by Tenant, even though minor items (i.e. punch
list) may remain to be installed, finished or corrected, provided the same do
not materially interfere with Tenant's use and occupancy of the Premises for the
conduct of its business. The date the Tenant's Work is Substantially Complete
shall be deemed the "Substantial Completion Date." Tenant shall cause the
General Contractor to diligently complete any items of work not completed when
the Premises are Substantially Complete. In the event of any dispute as to
Substantial Completion of the Tenant's Work, the Statement of the Tenant's
Architect shall be conclusive. Substantial Completion shall have occurred
notwithstanding punch list items.

10. CHANGES. Tenant may request reasonable changes in the Drawings; provided,
however, that (a) no change shall be made to the Drawings without Landlord's
Representative's prior written approval, which approval shall not be
unreasonably withheld or delayed; (b) no such request shall effect any
structural change in the Buildings or otherwise render the Premises or Buildings
in violation of applicable laws; (c) Tenant shall pay any additional costs
required to implement such change, including, without limitation, architecture
and other consultant fees, increases in construction costs and other charges
payable caused (to the extent they are not covered by the Landlord's
Contribution); and (d) such requests shall constitute an agreement by Tenant to
any delay in completion caused by Landlord's reviewing, processing and
implementing such change. If Tenant requests or causes any change, addition or
deletion to the Premises to be necessary after approval of the Drawing, a
request for the change shall be submitted to Landlord's Representative,
accompanied by revised plans prepared by the Tenant's Architect, all at Tenant's
sole expense (to the extent not covered by Landlord's Contribution). Tenant
acknowledges that neither the Tenant's Architect nor any contractor engaged by
Tenant is Landlord's agent and neither entity has authority to enter into
agreements on Landlord's behalf or otherwise bind Landlord.

11. TENANT'S REPRESENTATIVE. Tenant has designated the Tenant's Representative
as its sole representative with respect to the matters set forth in this Work
Letter, who shall have full authority and responsibility to act on behalf of the
Tenant as required in this Work Letter. Tenant shall not change the Tenant's
Representative without notice to Landlord.

12. LANDLORD'S REPRESENTATIVE. Landlord has designated Landlord's Representative
as its sole representative with respect to the matters set forth in this Work
Letter, who shall have full authority and responsibility to act on behalf of
Landlord as required in this Work Letter. Landlord shall not change Landlord's
Representative without notice to Tenant.

13. NO REPRESENTATIONS OR WARRANTIES. Notwithstanding anything to the contrary
contained in the Lease or herein, Landlord's participation in the preparation of
the Drawings, the cost estimates for the Tenant's Work and the construction of
the Tenant's Work shall not constitute any representation or warranty, express
or implied, that (i) the Drawings are in conformity with applicable governmental
codes, regulations or rules or (ii) that the Tenant's Work, if built in
accordance with the Drawings, will be suitable for Tenant's intended purpose.
Tenant acknowledges and agrees that the Tenant's Work are intended for use by
Tenant and the specification and design requirements for such improvements are
not within the special knowledge or experience of Landlord. Landlord's
obligations shall be to review the Drawings; and any additional cost or expense
required for the modification thereof to more adequately meet Tenant's use,
whether during or after construction thereof, shall be borne entirely by Tenant.


                                      F-5
<PAGE>

14. INCORPORATION. This Work Letter and all schedules attached hereto are
incorporated in the Lease; and all of the terms and provisions of the Lease are
incorporated herein by this reference.

                                   "Landlord"

                                   NEW ALLIANCE PROPERTIES, INC.,
                                   a Delaware corporation


                                   By: /s/ Douglas McCormick
                                      ----------------------------------
                                   As its: Chief Financial Officer
                                          ------------------------------


                                   Tenant

                                   LIGHTBRIDGE, INC., a Delaware corporation


                                   By: /s/ Joseph S. Tibbetts Jr.
                                      ---------------------------------------
                                   As its: SRVP & CFO
                                          ------------------------------


                                      F-6
<PAGE>

                                    EXHIBIT D
                              RULES AND REGULATIONS

      It is further agreed that the following rules and regulations shall be and
are hereby made a part of this Lease and Tenant agrees that Tenant's employees
and agents or any others permitted by Tenant to occupy or enter the Premises
will at all times abide by these rules and regulations as they may be amended or
supplemented from time to time. Capitalized terms have the same meaning as used
in the Lease, unless otherwise indicated.

(1)   The sidewalks, entries, passages, corridors, and stairways of the Building
      Complex shall not be obstructed or locked or used for smoking, storage or
      loitering by Tenant or Tenant's agents or employees or used for any
      purpose other than ingress and egress to and from the Premises.

(2)   Furniture, equipment, or supplies will be moved in or out of the Building
      only through access ways designated by Landlord and then only during such
      hours and in such manner as may be prescribed by Landlord. The Landlord
      shall have the right to reasonably approve or disapprove the movers or
      moving company employed by Tenant and Tenant shall cause the movers to use
      only the loading facilities and access ways designated by Landlord. In the
      event Tenant's movers damage any part of the Building, Tenant shall
      forthwith pay to Landlord the amount required to repair that damage to the
      extent not covered by insurance maintained on the Building.

(3)   No safe or article, the weight of which may, in the opinion of Landlord,
      constitute a hazard or damage to the Building or the Building's equipment,
      shall be moved into the Premises. Safes and other equipment, the weight of
      which is not excessive, shall be moved into, from, or about the Building
      only during such hours and in such manner as shall be prescribed by
      Landlord and landlord shall have the right to designate the location of
      such articles in the Premises.

(4)   Except for the signs permitted under the terms of the Lease, no sign,
      advertisement or notice shall be inscribed, painted, or affixed on any
      part of the inside or outside of the Building (including windows) unless
      of such color, size, and style and in such place upon or in the Building
      as shall be first designated by Landlord in writing but there shall be no
      obligation or duty on Landlord to allow any sign, advertisement or notice
      to be inscribed, painted, or affixed on any part of the inside or outside
      of the building other than the Building standard approved Tenant signs. No
      furniture shall be placed in front of the Building or in any lobby or
      corridor of the building (whether included wholly within the Premises, or
      otherwise), without the prior written consent of Landlord. Landlord shall
      have the right to remove all non-permitted signs and furniture, without
      notice to Tenant, at the expense of Tenant.

(5)   Tenant shall not do or permit anything to be done in the Premises or bring
      or keep anything therein which would in any way increase the rate of fire
      insurance on the Building, constitute a nuisance or waste, obstruct or
      interfere with the rights of other tenants or in any way injure or annoy
      them, or conflict with the laws relating to fire or with any regulations
      of the fire department, fire insurance underwriters, or with any insurance
      policy upon the Building or any part thereof, or conflict with any of the
      rules or ordinances of the Department of Health of the City and County
      where the Building is located.

(6)   The janitor of the building may at all times keep a passkey and subject to
      the prior notice requirements of the Lease, other agents of Landlord shall
      at all times be allowed admittance to the Premises.

(7)   Water closets and other water fixtures shall not be used for any purpose
      other than that for which they were intended and any damage resulting to
      them from misuse on the part of Tenant or Tenant's agents or employees
      shall be paid for by Tenant. No person shall waste water by tying back or
      wedging the faucets or in any other manner.

(8)   Except for handicapped assistance dogs, no animals shall be allowed in the
      offices, halls, and corridors in the Building. No person shall disturb the
      occupants of the Building or adjoining buildings or premises by the use of
      any radio, sound equipment, or musical instrument or by the making of loud
      or improper noises.

(9)   Bicycles shall be permitted in the Building so long as they are stored in
      designated areas such as a storage room.
<PAGE>

(10)  Tenant shall not allow anything to be placed on the outside of the
      building, nor shall anything be thrown by Tenant or Tenant's agents or
      employees out of the windows or doors or down the corridors, or
      ventilating ducts of the Building. Tenant, except in case of fire or other
      emergency, shall not open any outside window. Tenant must at its own
      expense dispose of crates, boxes, or similar large items of refuse which
      will not fit into office waste paper baskets. In no event shall Tenant set
      any such items in the corridors or other areas of the Building.

(11)  No additional lock or locks shall be placed by Tenant on any door in the
      Building, unless written consent of Landlord shall first have been
      obtained. Two keys to the Premises and the toilet rooms, if locked by
      Landlord, will be furnished by Landlord and neither Tenant nor Tenant's
      agents or employees shall have any duplicate keys made. Landlord shall
      supply Tenant with such additional keys as Tenant may require at Tenant's
      sole cost and expense. At the termination of this tenancy, Tenant shall
      promptly return to Landlord all keys to offices, toilet rooms, or vaults.

(12)  No window shades, blinds, screens, draperies, or other window coverings
      will be attached or detached by Tenant without Landlord's prior written
      consent. Tenant agrees to abide by Landlord's rules with respect to
      maintaining uniform curtains, draperies and linings, or blinds at all
      windows and hallways.

(13)  If any Tenant desires telegraphic, telephonic, or other electric
      connections, Landlord or Landlord's agents will direct the electricians as
      to where and how the wires may be introduced. Without such directions, no
      boring or cutting for wires will be permitted. Any such installation and
      connection shall be made at Tenant's expense.

(14)  Tenant shall not install or operate any steam or gas engine or boiler or
      carry on any mechanical business in the Premises. The use of oil, gas, or
      inflammable liquids for heating, lighting, or any other purpose is
      expressly prohibited. Explosives or other articles deemed extra hazardous
      shall not be brought into the Building.

(15)  Any painting or decorating, as may be agreed to be done by and at the
      expense of Landlord, shall be done during regular weekday working hours.
      Should Tenant desire such work on Saturdays, Sundays, Legal Holidays, or
      outside of regular working hours, Tenant shall pay for the extra cost
      thereof.

(16)  Except as permitted by Landlord and except for pictures, artwork and other
      decorating items, Tenant shall not mark upon, paint signs upon, cut drill
      into, drive nails or screws into, or in any way deface the walls,
      ceilings, partitions, or floors of the Premises or of the Building and any
      defacement, damage, or injury caused by Tenant or Tenant's agents or
      employees shall be paid for by Tenant.

(17)  Smoking is prohibited in the Building, including all tenants' premises,
      inside lobbies, bathrooms, and other Common Areas and public areas of the
      Building Complex and is restricted in all outside plaza areas of the
      Building Complex to specific locations designated by Landlord as smoking
      areas, if any.

(18)  Tenant shall be entitled to two sets of keys to the Premises. In the event
      Tenant needs any additional keys, such keys must be requested from
      Landlord. Tenant shall pay to Landlord the actual cost of making such
      additional keys. In case of fire, invasion, riot, public excitement or
      other commotion, Landlord also reserves the right to prevent access to the
      Building while it continues. Landlord shall in no case be liable for
      damages for the admission or exclusion of any person to or from the
      Building.

(19)  No canvassing, soliciting, distribution of hand bills or other written
      material, or peddling shall be permitted in the Building on the Building
      Complex, and Tenant shall cooperate with Landlord in prevention and
      elimination of same.


                                      D-2
<PAGE>

                                    EXHIBIT E
                         LEASE COMMENCEMENT CERTIFICATE

LANDLORD:   NEW ALLIANCE PROPERTIES, INC., a Delaware corporation

TENANT:     LIGHTBRIDGE, INC., a Delaware corporation

      This Lease Commencement Certificate is made by Landlord and Tenant
pursuant to that certain Office Lease (the "Lease") entered into as of
_____________________,____, for the Leased Premises known as Suite _______, in
the Building known as 275 Interlocken Boulevard (the "Premises"). This
constitutes a supplementary addendum to the Lease as contemplated by Article 4
of the Lease.

      1. Lease Commencement Date. Landlord and Tenant acknowledge and agree that
the Lease Commencement Date, as contemplated by Article 4 of the Lease, is
___________________, __ and the Lease Expiration Date is ___________________,
__. Rent as contemplated by the Lease begins accruing to Landlord's benefit as
of ___________________, __. All covenants in the Lease contemplated to begin on
the Lease Commencement Date shall commence as of the Lease Commencement Date.

      2. Incorporation in Lease. This Certificate is incorporated into the
Lease, and forms a supplementary and integral part thereof. This Certificate
shall be construed and interpreted in accordance with all other terms and
provisions of the Lease for all purposes.

                                    Landlord

                                    NEW ALLIANCE PROPERTIES, INC.,
                                    a Delaware corporation

                                    By:______________________________________
                                    As its:__________________________________


                                    Tenant

                                    LIGHTBRIDGE, INC., a Delaware corporation

                                    By:______________________________________
                                    As its:__________________________________

Attest:

By:________________________
Title:_____________________