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	Number  
 	 	WARRANTS NOT EXERCISED ON OR BEFORE 5:00 P.M.,

MINNEAPOLIS TIME, ON SEPTEMBER 29, 2003 SHALL BECOME VOID	 	Warrants  
 
	 
 

 
 WS-                   	 
 	 
 OXBORO MEDICAL, INC.
 INCORPORATED UNDER THE LAWS OF THE STATE OF MINNESOTA
 WARRANT CERTIFICATE	 
 	 
                      

 
 
	THIS CERTIFIES THAT	 	 	 	 
	 
  	 
 	 

WARRANTS CUSIP
	 

, OR REGISTERED ASSIGNS,

IS THE REGISTERED HOLDER OF

	 
 	 

 	 
 	 

 

***                   *** 

(the
"Warrants"), expiring at 5:00 p.m., Minneapolis time, on September 29, 2003 (the "Expiration Date"), to purchase Common Stock, $.01 par value per share (the "Common Stock"), of OXBORO
MEDICAL, INC., a Minnesota corporation (the "Company"). The Warrants may be exercised at any time from 9:00 a.m., Minneapolis time, on       to 5:00 p.m., Minneapolis time, on the
Expiration Date. Each Warrant entitles the holder upon exercise to receive from the Company, if exercised before 5:00 p.m., Minneapolis time, on the Expiration Date, one fully paid and nonassessable
share of Common Stock (a "Warrant Share") at the Exercise Price (as defined in the Warrant Agreement referred to below), payable in lawful money of the United States of America, upon surrender of this
Warrant Certificate and payment of the Exercise Price at the office or agency of the Warrant Agent but only subject to the conditions set forth herein and in the Warrant Agreement. The Exercise Price
and number of Warrant Shares issuable upon exercise of the Warrants are subject to adjustment upon the occurrence of certain events as set forth in the Warrant Agreement. 

  The
Warrants evidenced by this Warrant Certificate are part of a duly authorized issue of Warrants expiring on the Expiration Date entitling the holder on exercise to receive shares
of Common Stock of the Company and are issued or to be issued pursuant to a Warrant Agreement dated as of       , 2000 (the "Warrant Agreement'), duly executed and delivered by the Company
to WELLS FARGO BANK MINNESOTA, N.A., a national banking association, as Warrant Agent (the "Warrant Agent"), which Warrant Agreement is hereby incorporated by reference in and made a part of this
instrument and is hereby referred to for a description of the rights, limitation of rights, obligations, duties and immunities thereunder of the Warrant Agent, the Company and the holders (the words
"holders" or "holder" meaning the registered holders or registered holder) of the Warrants. A copy of the Warrant Agreement may be obtained by the holder hereof upon written request to the Company. By
accepting initial delivery, transfer or exchange of this Warrant, the duly registered holder shall be deemed to have agreed to the terms of the Warrant Agreement as it may be in effect from time to
time, including any amendments or supplements duly adopted in accordance therewith. 

  The
holder of Warrants evidenced by this Warrant Certificate may exercise them by surrendering this Warrant Certificate, with the Purchase Form on the reverse side hereof properly
completed and executed, together with payment of the Exercise Price in the manner described below at the office of the Warrant Agent. In the event that upon any exercise of Warrants evidenced hereby
the number of Warrants exercised shall be less than the total number of Warrants evidenced hereby, there shall be issued to the holder hereof or its assignee a new Warrant Certificate evidencing the
number of Warrants not exercised. 

  Payment
of the Exercise Price may be made in cash by wire transfer to the Warrant Agent for the account of the Company or by certified or official bank check or checks to the order to
the Company or by any combination thereof. 

  The
Warrant Agreement provides that upon the occurrence of certain events the number of shares of Common Stock issuable upon the exercise of each Warrant, and the Exercise Price of
each Warrant, may, subject to certain conditions, be adjusted. No fractions of a share of Common Stock will be issued upon the exercise of any Warrant, but the Company shall pay the cash value thereof
determined as provided in the Warrant Agreement. 

  Warrant
Certificates, when surrendered at the office of the Warrant Agent by the registered holder thereof in person or by legal representative or attorney duly authorized in writing,
may be exchanged, in the manner and subject to the limitations provided in the Warrant Agreement, but without payment of any service charge, for another warrant Certificate or Warrant Certificates of
like tenor evidencing in the aggregate a like number of Warrants. 

  Upon
due presentation for registration of transfer of this Warrant Certificate at the office of the Warrant Agent, a new Warrant Certificate or Warrant Certificates of like tenor and
evidencing in the aggregate a like number of Warrants shall be issued to the transferee(s) in exchange of this Warrant Certificate, subject to the limitations provided in the Warrant Agreement,
without charge except for any tax or other governmental charge imposed in connection therewith. 

  The
Company and the Warrant Agent may deem and treat the registered holder(s) hereof as the absolute owner(s) of this Warrant Certificate (notwithstanding any notation of ownership or
other writing hereon made by anyone), for the purpose of any exercise hereof, of any distribution to the holder(s) hereof, and for all other purposes, and neither the Company nor the Warrant Agent
shall be affected by any notice to the contrary. Neither the Warrants nor this Warrant Certificate entitles any holder hereof to any rights of a stockholder of the Company. 

  This
Warrant Certificate shall not be valid unless countersigned by the Warrant Agent, as such term is used in the Warrant Agreement. 

  WITNESS
the facsimile seal of the Company and the facsimile signatures of the Company's duly authorized officers. 

Dated:

	COUNTERSIGNED AND REGISTERED:	 	OXBORO MEDICAL, INC.	 
	WELLS FARGO BANK MINNESOTA, N.A.	 	BY	Attest:
	AS WARRANT AGENT	 	 	 
	 

 	 
 	 

 	 

 
	BY	 	

 	

 
	Authorized Signature	 	Its PRESIDENT	Its SECRETARY

 

TO:    Oxboro
Medical, Inc. 

Wells
Fargo Bank Minnesota, N.A., Warrant Agent 

  PURCHASE FORM
       (To be executed by the Registered Holder in Order to Exercise Warrant Certificates)        

    The
undersigned hereby irrevocably elects to exercise this Warrant, according to the terms and conditions hereof, and to purchase for cash
             Shares of Common Stock issuable upon exercise of this Warrant, and herewith makes payment of the exercise price $    thereof, and requests
that certificates for such Shares be issued in the name of the undersigned or his assignee as indicated on the Assignment Form below. 

	Please insert social security

or other identifying number of

registered holder of certificate
	 	
 (Name—Please Print)

 
 (Address)

 

	 

Dated:         	 
 	 

 (Signature)*
	 	 	* NOTICE—The signature(s) to the Purchase Form or the Assignment Form must correspond to the name as written upon the face of the Warrant Certificate in every particular without alteration or enlargement or any
change whatsoever.

*    *    *    *

  ASSIGNMENT FORM
       (To be Executed By the Registered Holder in Order to Transfer the Warrant)        

    FOR
VALUE RECEIVED, the undersigned hereby sells, assigns, and transfers its right to purchase                     shares of Common Stock represented by
the attached Warrant Certificate unto

                                         
  

(Please print or type name and address, including postal zip code, of Assignee) 

(Social Security or other identifying number of assignee:                    ) and does irrevocably constitute and
appoint                                      attorney to
transfer the Warrant Certificate on the records of the Company with full power of substitution in the premises. 

Date:
                    ,        . 

	
 Social Security number of Assignee	 	Signature(s)*

	 

 	 
 	 

* NOTICE—The
signature(s) to the Purchase Form or the Assignment Form must correspond to the name as written upon the face of the Warrant Certificate in every particular
without alteration or enlargement or any change whatsoever. 

Signatures
Guaranteed:                                     

The
signature(s) should be guaranteed by an eligible guarantor institution (banks, stockbrokers, savings and loan associations and credit unions with membership in an approved medallion signature
guarantee program) pursuant to S.E.C. Rule 17Ad-15 

*    *    *    *

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PURCHASE FORM (To be executed by the Registered Holder in Order to Exercise Warrant Certificates)

ASSIGNMENT FORM (To be Executed By the Registered Holder in Order to Transfer the Warrant)<PAGE>
                                                                    Exhibit 10.1

                            TENTH AMENDMENT TO LEASE

      TENTH AMENDMENT TO LEASE dated as of this 20th day of April, 2000, by and
between BP PRUCENTER ACQUISITION, LLC, a Delaware limited liability company (as
successor-in-interest to The Prudential Insurance Company of America)
("Landlord") and DIGITAS LLC, formerly known as BRONNERCOM, LLC, formerly known
as BRONNER SLOSBERG HUMPHREY, LLC, a Delaware limited liability company, as
successor-in-interest to Bronner Slosberg Humphrey, Inc. ("Tenant").

                                    RECITALS

      By Lease dated May 31, 1995, as amended by a First Amendment of Lease
dated June 21, 1996, a Second Amendment of Lease dated September 1, 1996, a
Third Amendment of Lease dated November 5, 1996, a Fourth Amendment of Lease
dated January 22, 1997, a Fifth Amendment and Partial Termination of Lease dated
July 11, 1997, a Sixth Amendment and Partial Termination of Lease dated May 15,
1998, a Seventh Amendment to Lease dated March 29, 1999, an Eighth Amendment to
Lease dated July 30, 1999 and a Ninth Amendment to Lease dated February __, 2000
(the "Lease"), Landlord's predecessor-in-interest did lease to Tenant and Tenant
did hire and lease from Landlord's predecessor-in-interest certain premises (the
"Initial Premises") located in the Tower Building (the "Building"), Prudential
Center, Boston, Massachusetts, which Initial Premises are described with greater
particularity in the Lease.

      Tenant desires to hold options to lease additional premises in the
Building, to wit, Floor 4 and Floor 28, and to amend other provisions of the
Lease;

      Landlord is willing to grant such options to Tenant and to amend the Lease
on the terms and conditions hereinafter set forth;

      NOW THEREFORE, in consideration of One Dollar ($1.00) and other good and
valuable consideration in hand this date paid by each of the parties to the
other, the receipt and sufficiency of which are hereby severally acknowledged,
and in further consideration of the mutual promises herein contained, Landlord
and Tenant hereby agree to and with each other as follows:

      1.    FOURTH FLOOR EXPANSION OPTION

      Tenant shall have the right to increase the size of the Premises by adding
thereto Floor 4 of the Building containing 24,715 square feet of rentable floor
area (the "Fourth Floor Expansion Space") in the manner and subject to the terms
and conditions as hereinafter set forth.
<PAGE>

      If, as of the date of Tenant's Exercise Notice and as of the Commencement
Date in respect of the Fourth Floor Expansion Space, (i) Tenant is not in
default, beyond the expiration of applicable notice and grace periods, in the
performance of any obligations to be performed by Tenant under the Lease and
(ii) this Lease is still in full force and effect, Tenant shall have the right
to lease the Fourth Floor Expansion Area by giving Landlord written notice
("Tenant's Exercise Notice") on or before July 1, 2000 and Tenant's Exercise
Notice shall constitute an agreement to add the Fourth Floor Expansion Space to
the Premises demised under the Lease for a term coterminous with the Term of the
Lease upon all of the same terms, conditions, covenants and agreements contained
in the Lease except as follows:

      A.    The Commencement Date in respect of the Fourth Floor Expansion Space
            shall be the day after the date that the present tenant of the
            Fourth Floor Expansion Space vacates the Fourth Floor Expansion
            Space, which date is estimated to occur between September 1, 2001
            and December 31, 2001. Landlord shall give Tenant reasonable advance
            notice of the actual Commencement Date in respect of the Fourth
            Floor Expansion Space.

            If the Commencement Date in respect of the Fourth Floor Expansion
            Space has not occurred on or before September 30, 2001, then Tenant
            shall be entitled to a rent abatement against Tenant's obligation to
            pay rent in respect of the Fourth Floor Expansion Space equal to one
            (1) day for each day between October 1, 2001 and the Commencement
            Date in respect of the Fourth Floor Expansion Space. Such abatement
            shall be in addition to any delay in Tenant's obligation to pay rent
            in respect of the Fourth Floor Expansion Space based on the
            Commencement Date in respect of the Fourth Floor Expansion Space.
            For example, if the Commencement Date in respect of the Fourth Floor
            Expansion Space occurs on October 15, 2001, then Tenant's obligation
            to pay rent in respect of the Fourth Floor Expansion Space shall not
            commence until November 1, 2001 (i.e., 15 days after such
            Commencement Date). If the Commencement Date in respect of the
            Fourth Floor Expansion Space has not occurred on or before December
            31, 2001, Tenant shall have the right to terminate the Lease with
            respect to the Fourth Floor Expansion Space only, by giving notice
            to Landlord of Tenant's desire to do so on or before January 31,
            2002; and upon the giving of such notice, the Lease shall terminate
            with respect to the Fourth Floor Expansion Space only, without
            further liability or obligation on the part of either party, unless
            within thirty (30) days after receipt of such termination notice
            from Tenant, the Commencement Date in respect of the Fourth Floor
            Expansion Space has occurred.

                                       -2-
<PAGE>

            Such rent abatement and right of termination shall be Tenant's sole
            and exclusive remedies at law or in equity or otherwise for the
            failure of the Commencement Date in respect of the Fourth Floor
            Expansion Space to occur by September 30, 2001 or December 31, 2001,
            respectively.

      B.    The Term of the Lease for the Fourth Floor Expansion Space shall
            commence on the Commencement Date in respect of the Fourth Floor
            Expansion Space and shall expire on November 30, 2005, unless sooner
            terminated in accordance with the provisions of the Lease as herein
            amended, upon all the same terms and conditions contained in the
            Lease as herein amended.

      C.    Tenant's obligation to pay rent, Increased Operating Expenses and
            increased Real Estate Taxes in respect of the Fourth Floor Expansion
            Space shall commence to accrue on the Commencement Date in respect
            of the Fourth Floor Expansion Space.

      D.    Rent for the Fourth Floor Expansion Space shall be payable at the
            annual rate of $1,161,605.00 (being the product of (i) $47.00 and
            (ii) the rentable floor area of the Fourth Floor Expansion Space
            (being 24,715 square feet).

      E.    Commencing on the Commencement Date in respect of the Fourth Floor
            Expansion Space, Tenant shall reimburse Landlord for Increased
            Operating Expenses (pursuant to Section 3.2 of the Lease) for the
            Fourth Floor Expansion Space in excess of the Operating Expenses
            incurred by Landlord during calendar year 2001 (being January 1,
            2001 through December 31, 2001).

      F.    Commencing on the Commencement Date in respect of the Fourth Floor
            Expansion Space, Tenant shall reimburse Landlord for increased Real
            Estate Taxes (pursuant to Section 3.4 of the Lease) for the Fourth
            Floor Expansion Space in excess of the Real Estate Taxes paid by
            Landlord in fiscal year 2002 (being July 1, 2001 through June 30,
            2002).

      G.    Tenant's Share with respect to the Fourth Floor Expansion Space
            consisting of a total of 24,715 rentable square feet will be 2.02%.

      H.    Tenant shall reimburse Landlord monthly in arrears within thirty
            (30) days of receipt of Landlord's invoice for the cost of
            electricity consumed in the Fourth Floor Expansion Space as
            determined by a check meter (which check meter is presently
            installed) at Landlord's cost of electricity from time to time.

      I.    As provided in the Lease, on the Commencement Date in respect of the
            Fourth

                                       -3-

<PAGE>

            Floor Expansion Space, Tenant shall be entitled to lease (i) up
            to twelve (12) additional non-reserved parking spaces at the then
            current monthly rates for non-reserved spaces, and (ii) one (1)
            reserved parking space at the then current monthly rate for
            reserved spaces. All of such spaces shall be leased from the
            Prudential Center garage operator in addition to those currently
            leased by Tenant.

      J.    Tenant's extension rights set forth in Section 12.15 of the
            Lease, as amended by Section II(1) of the Fourth Amendment of
            Lease, shall apply to the Fourth Floor Expansion Space.

      K.    Tenant shall lease the Fourth Floor Expansion Space in "as-is"
            condition, broom clean and clear of all occupants, in the condition
            in which the Fourth Floor Expansion Space is in as of the
            Commencement Date in respect of the Fourth Floor Expansion Space,
            without any obligation on the part of Landlord to prepare or
            construct the Fourth Floor Expansion Space for Tenant's occupancy,
            except that Landlord shall provide to Tenant an allowance of $15.00
            per square foot of rentable floor area of the Fourth Floor
            Expansion Space (the "Fourth Floor Expansion Space Allowance")
            towards the cost of design and improvements (including, without
            limitation, telephone and data wiring) to be performed by Tenant in
            the Fourth Floor Expansion Space in accordance with the terms of
            the Lease after Tenant delivers to Landlord paid invoices
            indicating the actual cost of such design and improvements
            reasonably satisfactory to Landlord. Notwithstanding the foregoing,
            Landlord shall be under no obligation to apply any portion of the
            Fourth Floor Expansion Space Allowance for any purposes other than
            as provided in this Paragraph 1.K, nor shall Landlord be deemed to
            have assumed any obligations, in whole or in part, of Tenant to any
            contractors, subcontractors, suppliers, workmen or materialmen. In
            addition, Landlord shall not be obligated to make any application
            of any portion of the Fourth Floor Expansion Space Allowance if
            (i) there shall be existing any default of Tenant under the Lease
            (as defined in Section 8.1), beyond the expiration of applicable
            notice and grace periods, or (ii) there are any liens which are
            not bonded to the reasonable satisfaction of the Landlord against
            Tenant's interest in the Lease or against the Premises, the
            Building, or the Prudential Center arising out of any work
            performed pursuant to the Lease by Tenant or any litigation in
            which Tenant is a party.

       L.   There shall be no increase in the Replacement LC, as hereinafter
            defined, in connection with Tenant's demise of the Fourth Floor
            Expansion Space.

       If Tenant fails timely to give Tenant's Exercise Notice, Tenant shall
have no right to

                                       -4-
<PAGE>

lease the Fourth Floor Expansion Space and the terms of this Paragraph 1 shall
be null and void, time being of the essence hereof.

      2.    TWENTY-EIGHTH FLOOR EXPANSION OPTION

      Tenant shall have the right to increase the size of the Premises by adding
thereto Floor 28 of the Building containing 25,676 square feet of rentable floor
area (the "Twenty-Eighth Floor Expansion Space") in the manner and subject to
the terms and conditions as hereinafter set forth.

      If as of the date of Tenant's Exercise Notice and as of the Commencement
Date in respect of the Twenty-Eighth Floor Expansion Space, (i) Tenant is not in
default, beyond the expiration of applicable notice and grace periods, in the
performance of any obligations to be performed by Tenant under the Lease and
(ii) this Lease is still in full force and effect, Tenant shall have the right
to lease the Twenty-Eighth Floor Expansion Area by giving Landlord written
notice ("Tenant's Exercise Notice") on or before January 1, 2001 and Tenant's
Exercise Notice shall constitute an agreement to add the Twenty-Eighth Floor
Expansion Space to the Premises demised under the Lease for a term coterminous
with the Term of the Lease upon all of the same terms, conditions, covenants and
agreements contained in the Lease except as follows:

      A.    The Commencement Date in respect of the Twenty-Eighth Floor
            Expansion Space shall be the day after the date that the present
            tenant of the Twenty- Eighth Floor Expansion Space vacates the
            Twenty-Eighth Floor Expansion Space, which date is estimated to
            occur between September 1, 2001 and December 31, 2001. Landlord
            shall give Tenant reasonable advance notice of the actual
            Commencement Date in respect of the Twenty-Eighth Floor Expansion
            Space.

            If the Commencement Date in respect of the Twenty-Eighth Floor
            Expansion Space has not occurred on or before September 30, 2001,
            then Tenant shall be entitled to a rent abatement against Tenant's
            obligation to pay rent in respect of the Twenty-Eighth Floor
            Expansion Space equal to one (1) day for each day between October 1,
            2001 and the Commencement Date in respect of the Twenty-Eighth Floor
            Expansion Space. Such abatement shall be in addition to any delay in
            Tenant's obligation to pay rent in respect of the Twenty-Eighth
            Floor Expansion Space based on the Commencement Date in respect of
            the Twenty-Eighth Floor Commencement Date. For example, if the
            Commencement Date in respect of the Twenty-Eighth Floor Expansion
            Space occurs on October 15, 2001, then Tenant's obligation to pay
            rent in respect of the Fourth Floor Expansion Space shall not
            commence until November 1, 2001 (i.e., 15 days after such
            Commencement Date). If the Commencement

                                       -5-
<PAGE>

            Date in respect of the Twenty-Eighth Floor Expansion Space has not
            occurred on or before December 31, 2001, Tenant shall have the right
            to terminate the Lease with respect to the Twenty-Eighth Floor
            Expansion Space only, by giving notice to Landlord of Tenant's
            desire to do so on or before January 31, 2002; and upon the giving
            of such notice, the Lease shall terminate with respect to the
            Twenty-Eighth Floor Expansion Space only, without further liability
            or obligation on the part of either party, unless within thirty (30)
            days after receipt of such termination notice from Tenant, the
            Commencement Date in respect of the Twenty-Eighth Floor Expansion
            Space has occurred.

            Such rent abatement and right of termination shall be Tenant's sole
            and exclusive remedies at law or in equity or otherwise for the
            failure of the Commencement Date in respect of the Twenty-Eighth
            Floor Expansion Space to occur by September 30, 2001 or December 31,
            2001, respectively.

      B.    The Term of the Lease for the Twenty-Eighth Floor Expansion Space
            shall commence on the Commencement Date in respect of the
            Twenty-Eighth Floor Expansion Space and shall expire on November 30,
            2005, unless sooner terminated in accordance with the provisions of
            the Lease as herein amended, upon all the same terms and conditions
            contained in the Lease as herein amended.

      C.    Tenant's obligation to pay rent, Increased Operating Expenses and
            increased Real Estate Taxes in respect of the Twenty-Eighth Floor
            Expansion Space shall commence to accrue on the Commencement Date in
            respect of the Twenty-Eighth Floor Expansion Space.

      D.    Rent for the Twenty-Eighth Floor Expansion Space shall be payable at
            the annual rate of $1,347,990.00 (being the product of (i) $52.50
            and (ii) the rentable floor area of the Twenty-Eighth Floor
            Expansion Space (being 25,676 square feet).

      E.    Commencing on the Commencement Date in respect of the Twenty-Eighth
            Floor Expansion Space, Tenant shall reimburse Landlord for Increased
            Operating Expenses (pursuant to Section 3.2 of the Lease) for the
            Twenty- Eighth Floor Expansion Space in excess of the Operating
            Expenses incurred by Landlord during calendar year 2001 (being
            January 1,2001 through December 31, 2001).

      F.    Commencing on the Commencement Date in respect of the Twenty-Eighth
            Floor Expansion Space, Tenant shall reimburse Landlord for increased
            Real Estate Taxes (pursuant to Section 3.4 of the Lease) for the
            Twenty-Eighth

                                       -6-
<PAGE>

            Floor Expansion Space in excess of the Real Estate Taxes paid by
            Landlord in fiscal year 2002 (being July 1, 2001 through June 30,
            2002).

      G.    Tenant's Share with respect to the Twenty-Eighth Floor Expansion
            Space consisting of a total of 25,676 rentable square feet will be
            2.09%.

      H.    Tenant shall reimburse Landlord monthly in arrears within thirty
            (30) days of receipt of Landlord's invoice for the cost of
            electricity consumed in the Twenty-Eighth Floor Expansion Space as
            determined by a check meter (which check meter is presently
            installed) at Landlord's cost of electricity from time to time.

      I.    As provided in the Lease, on the Commencement Date in respect of the
            Twenty-Eighth Floor Expansion Space, Tenant shall be entitled to
            lease (i) up to twelve (12) additional non-reserved parking spaces
            at the then current monthly rates for non-reserved spaces, and (ii)
            one (1) reserved parking space at the then current monthly rate for
            reserved spaces. All of such spaces shall be leased from the
            Prudential Center garage operator in addition to those currently
            leased by Tenant.

      J.    Tenant's extension rights set forth in Section 12.15 of the Lease,
            as amended by Section II(1) of the Fourth Amendment of Lease, shall
            apply to the Twenty-Eighth Floor Expansion Space.

      K.    Tenant shall lease the Twenty-Eighth Floor Expansion Space in
            "as-is" condition, broom clean and clear of all occupants, in the
            condition in which the Twenty-Eighth Floor Expansion Space is in as
            of the Commencement Date in respect of the Twenty-Eighth Floor
            Expansion Space, without any obligation on the part of Landlord to
            prepare or construct the Twenty-Eighth Floor Expansion Space for
            Tenant's occupancy, except that Landlord shall provide to Tenant an
            allowance of $15.00 per square foot of rentable floor area of the
            Twenty-Eighth Floor Expansion Space (the "Twenty-Eighth Floor
            Expansion Space Allowance") towards the cost of design and
            improvements (including, without limitation, telephone and data
            wiring) to be performed by Tenant in the Twenty-Eighth Floor
            Expansion Space in accordance with the terms of the Lease after
            Tenant delivers to Landlord paid invoices indicating the actual cost
            of such design and improvements reasonably satisfactory to Landlord.
            Notwithstanding the foregoing, Landlord shall be under no obligation
            to apply any portion of the Twenty-Eighth Floor Expansion Space
            Allowance for any purposes other than as provided in this Paragraph
            2.K, nor shall Landlord be deemed to have assumed any obligations,
            in whole or in part, of Tenant to any contractors, subcontractors,
            suppliers, workmen or

                                       -7-
<PAGE>

            materialmen. In addition, Landlord shall not be obligated to make
            any application of any portion of the Twenty-Eighth Floor Expansion
            Space Allowance if (i) there shall be existing any default of Tenant
            under the Lease (as defined in Section 8.1), beyond the expiration
            of applicable notice and grace periods, or (ii) there are any liens
            which are not bonded to the reasonable satisfaction of the Landlord
            against Tenant's interest in the Lease or against the Premises, the
            Building, or the Prudential Center arising out of any work performed
            pursuant to the Lease by Tenant or any litigation in which Tenant is
            a party.

      L.    There shall be no increase in the Replacement LC, as hereinafter
            defined, in connection with Tenant's demise of the Twenty-Eighth
            Floor Expansion Space.

      If Tenant fails timely to give Tenant's Exercise Notice, Tenant shall have
no right to lease the Twenty-Eighth Floor Expansion Space and the terms of this
Paragraph 2 shall be null and void, time being of the essence hereof.

      3.    DELETION OF TENANT'S FIFTH YEAR OPTION TO EXPAND

      In consideration of the Expansion Options granted to Tenant in this Tenth
Amendment, the parties hereby confirm and agree that Tenant shall have no right
to add one additional floor to the Premises at the end of the fifth year
pursuant to Paragraph B of Section 12.16. Therefore, Paragraph B of Section
12.16 of the Lease is hereby deleted in its entirety and is of no further force
or effect.

      4.    REDUCTION IN LETTERS OF CREDIT

      A. In accordance with Section 12.14 of the Lease (as amended by Section 9
of the First Amendment of Lease, and by Paragraph 12 of the Seventh Amendment to
Lease), Tenant has delivered to Landlord an irrevocable standby letter of credit
in the original face amount of Four Million Seventy-Eight Thousand and 00/100
Dollars ($4,078,000.00) (the "Original LC") to secure, among other things, a
portion of the Lease Transaction Costs incurred by Landlord in connection with
the Initial Premises and the First Amendment Spaces. Section 12.14 (as amended
by Section 9 of the First Amendment of Lease and by Paragraph 12 of the Seventh
Amendment to Lease) also provides in part for yearly reductions of the Original
LC subject to the conditions contained in Section 12.14 of the Lease (as amended
by Section 9 of the First Amendment of Lease, and by Paragraph 12 of the Seventh
Amendment to Lease).

      B. In accordance with Section I(F) of the Third Amendment of Lease, as
amended by Paragraph 11 of the Seventh Amendment to Lease, the Tenant has
delivered to

                                       -8-
<PAGE>

Landlord an irrevocable standby letter of credit in the original face amount of
One Million Three Hundred Seventy-Five Thousand and 00/100 Dollars
($1,375,000.00) (the "Third Amendment LC") to secure, among other obligations of
Tenant under the Lease, a portion of the transaction costs incurred by Landlord
in connection with the twenty-fifth (25th) floor of the Building (the
"Twenty-Fifth Floor"). Paragraph 11 of the Seventh Amendment also provides in
part for the yearly reductions of the Third Amendment LC subject to the
conditions contained in said Paragraph 11.

      C. Notwithstanding anything to the contrary contained in the Lease, as so
amended, in consideration of the agreements contained in this Tenth Amendment,
Landlord shall, on the date ("Replacement LC Effective Date") that Landlord
receives the Replacement LC, as hereinafter defined, return to Tenant the Third
Amendment LC and the Original LC. In addition, upon Landlord's receipt of the
Replacement LC, Section 12.14 of the Lease, Paragraph 9 of the First Amendment
of Lease, Exhibit LCR to the First Amendment of Lease, Paragraph 1(F) of the
Third Amendment of Lease, Paragraphs 11 and 12 of the Seventh Amendment of Lease
and Exhibit LCR to the Seventh Amendment of Lease shall be deleted in their
entirety and the following Subparagraphs D, E, F, G and H shall govern the terms
of the Replacement LC.

      D. Tenant agrees that, upon Landlord's receipt of the Replacement LC, as
hereinafter defined, Landlord shall hold the same, throughout the term of the
Lease (including any extension thereof), as security for the performance by
Tenant of all obligations on the part of Tenant to be performed. Landlord shall
have the right from time to time without prejudice to any other remedy Landlord
may have on account thereof, to apply such deposit, or any part thereof, to
Landlord's damages arising from any default on the part of Tenant. If Landlord
so applies all or any portion of such deposit, Tenant shall within seven (7)
days after notice from Landlord deliver cash to Landlord in an amount sufficient
to restore the Replacement LC to the full amount stated herein. Tenant not then
being in default and having performed all of its obligations under this Lease,
including the payment of all annual rent, Landlord shall return the Replacement
LC, or so much thereof as shall not have theretofore been applied in accordance
with the terms hereof, to Tenant on the expiration or earlier termination of the
Term and surrender of possession of the Premises by Tenant to Landlord in the
condition required in the Lease at such time. If Landlord conveys Landlord's
interest under this Lease, the Replacement LC, or any part thereof not
previously applied, shall be turned over by Landlord to Landlord's grantee for
proper application of the Replacement LC in accordance with the terms of this
Paragraph 4, and the return thereof in accordance herewith, and Landlord shall
have no further liability therefor.

      E. Neither the holder of a mortgage nor the landlord in aground lease on
property which includes the Premises shall ever be responsible to Tenant for the
return or application of any such Replacement LC, whether or not it succeeds to
the position of Landlord hereunder, unless such Replacement LC shall have been
received in hand by such

                                       -9-
<PAGE>

holder or ground lessor.

      F. The "Replacement LC" shall be defined as an irrevocable letter of
credit, which shall: (a) be in the amount of One Million and 00/100
($1,000,000.00) Dollars; (b) be in the form attached hereto as Exhibit A, Tenth
Amendment, or in the form of the Third Amendment LC or the Original LC; (c) name
Landlord as its beneficiary; (d) be drawn on an FDIC insured financial
institution reasonably satisfactory to the Landlord; and (e) be renewable
automatically on an annual basis and expire no earlier than sixty (60) days
after the Termination Date of the Lease. If Landlord intends to assign
Landlord's interest in the Lease, Tenant shall, upon notice from Landlord,
deliver to Landlord an amendment to the Replacement LC naming Landlord's
assignee as the beneficiary thereof. If Tenant fails to deliver such amendment
within fifteen (15) days after notice from Landlord, Landlord shall have the
right to draw down the entire amount of the Replacement LC and hold the proceeds
thereof as a security deposit in accordance with this Paragraph 4.

      G. Notwithstanding anything herein to the contrary, the Replacement LC
shall be reduced by $100,000.00 per year commencing on the first (1st)
anniversary of the Replacement LC Effective Date, and on each anniversary
thereof, provided that all of the conditions set forth below ("Replacement LC
Reduction Conditions") are satisfied at the time of any reduction. Such
reduction shall be accomplished by having Tenant provide Landlord with a
substitute letter of credit in the reduced amount.

      H. The following Replacement LC Reduction Conditions must be satisfied at
the time of any reduction of the Replacement LC:

            (i)   Tenant must not be in default of any obligation under the
                  Lease beyond any applicable notice and cure period (including
                  Tenant's obligation to deliver cash to restore the Replacement
                  LC to the full amount in accordance with Paragraph 4.F
                  hereof);

            (ii)  Tenant shall have delivered to Landlord, within ninety (90)
                  days of the end of Tenant's fiscal year (1/1 - 12/31), a copy
                  of Tenant's financial statements for such fiscal year prepared
                  by a nationally recognized certified public accounting firm in
                  accordance with GAAP standards; and

            (iii) Tenant's tangible net worth, as determined in accordance with
                  generally accepted accounting principles, consistently
                  applied, as evidenced by Tenant's most recent financial
                  statements, is equal to or better than the tangible net worth
                  of Tenant, as determined in accordance with generally accepted
                  accounting principles, consistently applied, on the date of
                  this Tenth Amendment.

                                      -10-
<PAGE>

      If in any year during the term all the Replacement LC Reduction Conditions
are not satisfied as of the anniversary of the Replacement LC Effective Date for
such year, the Replacement LC shall not be reduced in such year. However, in
such event, the Replacement LC may be reduced on subsequent anniversaries of the
Replacement LC Effective Date if the Replacement LC Reduction Conditions are
satisfied for such year, provided however, that in no event shall the
Replacement LC be reduced by more than $100,000.00 in any one year.

      5.    SEVENTH AMENDMENT SPACE

      Reference is made to the Seventh Amendment Space, being the entirety of
the twenty-ninth (29th) floor of the Building consisting of 25,676 square feet
of rentable floor area, demised to Tenant pursuant to the Seventh Amendment to
Lease. Notwithstanding anything to the contrary in the Seventh Amendment to
Lease contained, the parties acknowledge that the present tenant of the Seventh
Amendment Space, Boston Edison, will remain in a portion of the Seventh
Amendment Space, to wit, two (2) telephone rooms, consisting of approximately
500 square feet of rentable floor area, as shown on the plan attached hereto as
Exhibit B, Tenth Amendment ("Area B"), for a period terminating no later than
June 30, 2001. Therefore, the Seventh Amendment Space shall consist of two (2)
areas (each, a "Portion"), being Area A, consisting of approximately 25,176
square feet of rentable floor area, and Area B. In implementation of this
Paragraph 5, Paragraphs 1 through 6 of the Seventh Amendment to Lease are hereby
deleted and the following are hereby substituted in their place:

      "1.   Effective as of the "Seventh Amendment Space Commencement Date" in
            respect of each Portion of the Seventh Amendment Space (as defined
            in Section 2 hereof) the Seventh Amendment Space shall constitute a
            part of the "Premises" (as defined and used in the Lease), so that
            the Premises (as defined and used in the Lease) shall include both
            the Initial Premises and the Seventh Amendment Space.

      2.    The Seventh Amendment Space Commencement Date in respect of each
            Portion of the Seventh Amendment Space shall be the earlier to occur
            of (a) the date on which such Portion of the Seventh Amendment Space
            is ready for occupancy as provided below or (b) the date on which
            Tenant commences beneficial use of such Portion of the Seventh
            Amendment Space (Tenant shall be treated as having commenced
            beneficial use when it begins to move furniture and equipment into
            such Portion of the Seventh Amendment Space for its regular business
            operation). Each Portion of the Seventh Amendment Space shall be
            deemed to be ready for occupancy at such time as Landlord shall have
            completed the "Asbestos Abatement Work" as described on Exhibit B
            attached hereto and placed such Portion of the Seventh Amendment
            Space

                                      -11-
<PAGE>

            in "shell condition" as described in Exhibit C to the
            above-referenced Fourth Amendment of Lease. Landlord shall give
            Tenant at least thirty (30) days prior written notice of the date on
            which Landlord anticipates that the work to be performed by Landlord
            hereunder will be completed and such Portion of the Seventh
            Amendment Space deemed ready for occupancy. Notwithstanding the
            foregoing, under no circumstances shall the Seventh Amendment Space
            Commencement Date in respect of either Portion be deemed to occur
            prior to March 1, 2001 (unless Tenant has commenced beneficial use
            of such Portion of the Seventh Amendment Space prior to that date).

            In the event that Landlord shall fail to deliver possession of Area
            A of the Seventh Amendment Space with the Asbestos Abatement Work
            complete and the Area A of the Seventh Amendment Space in shell
            condition by May 1, 2001, then Landlord shall, as and when received
            by Landlord, pay to Tenant one hundred percent (100%) of the
            Holdover Premium, as hereinafter defined, paid to Landlord by the
            existing tenant of the Seventh Amendment Space ("Existing Tenant").
            For the purposes hereof, the "Holdover Premium" shall be equal to
            the use and occupancy charge required to be paid by the Existing
            Tenant under its lease for any period of time during which such
            Existing Tenant remains in the Seventh Amendment Space after March
            31, 2001 less the sum of (x) the Minimum Rent and additional rent
            applicable to the Seventh Amendment Space prior to such holdover,
            and (y) to the extent not otherwise collected by Landlord from the
            Existing Tenant, the actual, out-of-pocket expenses incurred by
            Landlord in enforcing its rights against the Existing Tenant to
            obtain possession of the Seventh Amendment Space. Landlord hereby
            represents to Tenant that the use and occupancy charge required to
            be paid by the Existing Tenant under its lease from and after April
            1, 2001 is equal to 200% of the Minimum Rent and additional rent
            applicable to the Seventh Amendment Space prior to such holdover,
            and that the Minimum Rent payable by the Existing Tenant under its
            lease prior to such holdover is equal to $39.00 per rentable square
            foot of the Seventh Amendment Space per annum.

            In the event that Landlord shall fail to deliver possession of Area
            A of the Seventh Amendment Space with the Asbestos Abatement Work
            complete and the Area A of the Seventh Amendment Space in shell
            condition by July 1, 2001, Tenant shall have the right to terminate
            the Lease with respect to the Seventh Amendment Space only, by
            giving notice to Landlord of Tenant's desire to do so within thirty
            (30) days after such date; and, upon, the giving of such notice, the
            Lease shall terminate with respect to the Seventh Amendment Space
            only, without further liability or obligation on the part of either
            party,

                                      -12-
<PAGE>

            unless within thirty (30) days after receipt of such termination
            notice from Tenant, Landlord shall so deliver the Seventh Amendment
            Space in the condition required above. Such Holdover Premium and
            right of termination shall be Tenant's sole and exclusive remedies
            at law or in equity or otherwise for Landlord's failure to deliver
            the Seventh Amendment Space by May 1, 2001, or July 1, 2001,
            respectively.

      3.    The Term of the Lease for each Portion of the Seventh Amendment
            Space shall commence on the respective Seventh Amendment Space
            Commencement Date in respect of each Portion of the Seventh
            Amendment Space and (notwithstanding the fact that the Term of the
            Lease with respect to the Initial Premises may have previously
            expired as set forth in the Lease) shall expire on the last day of
            the sixtieth (60th) full calendar month subsequent to the Seventh
            Amendment Space Commencement Date in respect of Area A (plus the
            partial month, if any, following the Seventh Amendment Space
            Commencement Date in respect of Area A) (the "Seventh Amendment
            Space Lease Term"), unless sooner terminated in accordance with the
            provisions of the Lease as herein amended, upon all the same terms
            and conditions contained in the Lease as herein amended.

      4.    Rent for each Portion of the Seventh Amendment Space from the
            respective Seventh Amendment Space Commencement Date in respect of
            such Portion of the Seventh Amendment Space through the expiration
            of the Seventh Amendment Space Lease Term shall be payable at the
            annual rate equal to the product of (i) $52.50 and (ii) the rentable
            floor area of such Portion of the Seventh Amendment Space.

      5.    Commencing on the respective Seventh Amendment Space Commencement
            Date in respect of each Portion of the Seventh Amendment Space,
            Tenant shall reimburse Landlord for Increased Operating Expenses
            (pursuant to Section 3.2 of the Lease) for each Portion of the
            Seventh Amendment Space in excess of the Operating Expenses incurred
            by Landlord during calendar year 2000 (being January 1, 2000 through
            December 31, 2000).

      6.    Commencing on the respective Seventh Amendment Space Commencement
            Date in respect of each Portion of the Seventh Amendment Space,
            Tenant shall reimburse Landlord for increased Real Estate Taxes
            (pursuant to Section 3.4 of the Lease) for each Portion of the
            Seventh Amendment Space in excess of the Real Estate Taxes paid by
            Landlord in fiscal year 2001 (being July 1, 2000 through June 30,
            2001)."

      7.    Tenant's Share with respect to Area A of the Seventh Amendment Space

                                      -13-
<PAGE>

            consisting of 25,176 rentable square feet will be 2.05%. Tenant's
            Share with respect to Area B of the Seventh Amendment Space
            consisting of 500 rentable square feet will be .04%.

      8.    As provided in the Lease, on the Seventh Amendment Space
            Commencement Date in respect of Area A, Tenant shall be entitled to
            lease, at the then current monthly rates, up to thirteen (13)
            additional parking spaces from the Prudential Center garage operator
            in additional to those currently leased. The rate for monthly
            parking spaces as of January 1, 2000 is $295.00 per month.

      In the event that Boston Edison holds over in Area A of the Seventh
Amendment Space beyond March 31, 2001 or in Area B of the Seventh Amendment
Space beyond June 30, 2001, Landlord shall enforce all of its rights and
remedies, both at law and in equity, against Boston Edison on account of such
holdover.

      6.    OTHER TERMS

      A.    Tenant hereby acknowledges and confirms that the indemnity set forth
            in Section 11.1 of the Lease shall apply, and always has applied, to
            the use or occupancy by Tenant of the Premises in its entirety and
            to the acts or omissions of Tenant, its agents, employees or any
            contractors brought onto the Premises in its entirety by Tenant.

      B.    (i) Tenant warrants and represents that Tenant has not dealt with
            any broker in connection with the consummation of this Tenth
            Amendment other than Meredith & Grew (the "Recognized Broker"); and
            in the event any claim is made against Landlord relative to dealings
            by Tenant with brokers other than the Recognized Broker, Tenant
            shall defend the claim against Landlord with counsel of Tenant's
            selection first approved by Landlord (which approval will not be
            unreasonably withheld) and save harmless and indemnify Landlord on
            account of loss, cost or damage which may arise by reason of such
            claim.

            (ii) Landlord warrants and represents that Landlord has not dealt
            with any broker in connection with the consummation of this Tenth
            Amendment other than the Recognized Broker; and in the event any
            claim is made against Tenant relative to dealings by Landlord with
            brokers other than the Recognized Broker, Landlord shall defend the
            claim against Tenant with counsel of Landlord's selection and save
            harmless and indemnity Tenant on account of loss, cost or damage
            which may arise by reason of such claim. Landlord shall be
            responsible for paying the commission due to the Recognized Broker
            in connection with this Tenth Amendment.

                                      -14-
<PAGE>

      C.    Except as otherwise expressly provided herein, all capitalized terms
            used herein without definition shall have the same meanings as are
            set forth in the Lease.

      D.    Except as herein amended the Lease shall remain unchanged and in
            full force and effect. All references to the "Lease" shall be deemed
            to be references to the Lease as herein amended.

      EXECUTED as a sealed instrument as of the date and year first above
written.

WITNESS:                                 LANDLORD:

/s/ Susan G. Murphy
-------------------
                                         BP PRUCENTER ACQUISITION, LLC

                                         By: BOSTON PROPERTIES LIMITED
                                             PARTNERSHIP, its Manager

                                             By: BOSTON PROPERTIES, INC.,
                                                 its general partner

                                                 By /s/ Claude B. Hooper
                                                    ------------------------
                                                 Name Claude B. Hooper
                                                      ----------------------
                                                 Title Senior Vice President
                                                       ---------------------

WITNESS:                                     TENANT:

/s/ Marschall Smith                          DIGITAS LLC
-------------------

MARSCHALL SMITH                              By /s/ Michael Goss
Executive Vice President                        ---------------------------
                                             Name Michael Goss
                                                  -------------------------
                                             Title Executive Vice President
                                                   ------------------------

                                      -15-
<PAGE>

                           EXHIBIT A. TENTH AMENDMENT

                            FORM OF LETTER OF CREDIT

                         _______________________________
                         (Name of Financial Institution)

                                                       Irrevocable Standby
                                                       Letter of Credit
                                                       No. _____________________
                                                       Issuance Date:___________
                                                       Expiration Date:_________
                                                       Applicant:_______________

Beneficiary

BP Prucenter Acquisition LLC
c/o Boston Properties Limited Partnership
800 Boylston Street, Suite 400
Boston, Massachusetts 02199-8001

Ladies/Gentlemen:

      We hereby establish our Irrevocable Standby Letter of Credit in your favor
for the account of the above referenced Applicant in the initial amount of One
Million and 00/100 U.S. Dollars ($1,000,000.00) available for payment at sight
by your draft drawn on us when accompanied by the following documents:

1.    An original copy of this Irrevocable Standby Letter of Credit.

2.    Beneficiary's dated statement purportedly signed by one of its officers
      reading: "This draw in the amount of ______________________ U.S. Dollars
      ($_____________) under your Irrevocable Standby Letter of Credit No.
      ____________________ represents funds due and owing to us as a result of
      the Applicant's failure to comply with one or more of the terms of that
      certain lease by and between BP Prucenter Acquisition LLC, as landlord,
      and Digitas LLC, as tenant."

      It is a condition of this Irrevocable Standby Letter of Credit that it
will be considered automatically renewed for a one year period upon the
expiration date set forth above and upon each anniversary of such date, unless
at least sixty (60) days prior to such expiration date or applicable anniversary
thereof, we notify you in writing by certified mail, return

                                      -16-
<PAGE>

receipt requested, that we elect not to so renew this Irrevocable Standby Letter
of Credit.

      In addition to the foregoing, we understand and agree that you shall be
entitled to draw upon this Irrevocable Standby Letter of Credit in accordance
with 1. and 2. above in the event that we elect not to renew this Irrevocable
Standby Letter of Credit and, in addition, you provide us with a dated statement
purportedly signed by one of Beneficiary's officers stating that the Applicant
has failed to provide you with an acceptable substitute irrevocable standby
letter of credit in accordance with the terms of the above referenced lease. We
further acknowledge and agree that: (a) upon receipt of the documentation
required herein, we will honor your draws against this Irrevocable Standby
Letter of Credit without inquiry into the accuracy of Beneficiary's signed
statement and regardless of whether Applicant disputes the content of such
statement; (b) this Irrevocable Standby Letter of Credit shall permit partial
draws and, in the event you elect to draw upon less than the full stated amount
hereof, the stated amount of this Irrevocable Standby Letter of Credit shall be
automatically reduced by the amount of such partial draw; and (c) you shall be
entitled to assign your interest in this Irrevocable Standby Letter of Credit
from time to time without our approval and without charge. In the event of an
assignment, we reserve the right to require reasonable evidence of such
assignment as a condition to any draw hereunder.

      This Irrevocable Standby Letter of Credit is subject to the Uniform
Customs and Practice for Documentary Credits (1993 revision) ICC Publication No.
500.

      We hereby engage with you to honor drafts and documents drawn under and in
compliance with the terms of this Irrevocable Standby Letter of Credit.

      All communications to us with respect to this Irrevocable Standby Letter
of Credit must be addressed to our office located at
_________________________________________________________ to the attention of
______________________________.

                                            Very truly yours,

                                            --------------------

                                                   [name]
                                            --------------------

                                                   [title}
                                            --------------------

                                      -17-

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