Document:

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                                                                     Exhibit 4.1

                            CERTIFICATE OF AMENDMENT
                                       OF
                     RESTATED CERTIFICATE OF INCORPORATION

   Mercury Interactive Corporation, a corporation organized and existing under
and by virtue of the General Corporation Law of the State of Delaware,

   DOES HEREBY CERTIFY:

   FIRST: That at a meeting of the Board of Directors of Mercury Interactive
Corporation, resolutions were duly adopted setting forth a proposed amendment
of the Certificate of Incorporation of said corporation, declaring said
amendment to be advisable and calling a meeting of the stockholders of said
corporation for consideration thereof. The resolution setting forth the
proposed amendment is as follows:

   RESOLVED: that the Restated Certificate of Incorporation of this corporation
by amended by changing the first paragraph of the Article thereof numbered III
so that, as amended said first paragraph of said Article shall be and read as
follows:

   "This corporation is authorized to issue two classes of stock to be
designated, respectively, "Common Stock" and "Preferred Stock". The total
number of shares which the corporation is authorized to issue is One Hundred
and Twenty-five Million (125,000,000) shares. One Hundred and Twenty Million
(120,000,000) shares shall be Common Stock and Five Million (5,000,000) shares
shall be Preferred Stock, each with a par value of $.002 per share."

   SECOND: That thereafter, pursuant to resolution of its Board of Directors, a
meeting of the stockholders of said corporation was duly called and held, upon
notice in accordance with Section 222 of the General Corporation Law of the
state of Delaware at which meeting the necessary number of share as required by
statue were voted in favor of the amendment.

   THIRD: That said amendment was duly adopted in accordance with the
provisions of Section 242 of the General Corporation Law of the State of
Delaware.

   IN WITNESS WHEREOF, Mercury Interactive Corporation has caused this
certificate to be signed by Amnon Landan, its Chief Executive Officer, and
Sharlene Abrams, its Secretary, this 26th day of May, 1999.

                                                    /s/ Amnon Landan
                                          By: _________________________________
                                                  Chief Executive Officer

         /s/ Sharlene Abrams
Attest: _____________________________
               SecretaryEXHIBIT 10.6

                            ASSET PURCHASE AGREEMENT

     THIS  AGREEMENT is made as of this 13th day of April,  1998, by and between
Uranium  Power  Corporation,   a  Colorado  corporation  (the  "Purchaser")  and
Athabasca Uranium Syndicate, a syndicate formed in British Columbia, Canada (the
"Seller").

     WHEREAS,  the Seller is willing to sell,  and the  Purchaser  is willing to
purchase,  all  of the  assets  of  the  Seller  on  the  terms  and  conditions
hereinafter set forth.

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

     1.  Purchase  and Sale of the Assets.  The Seller  agrees to sell,  assign,
convey and transfer to the Purchaser,  and the Purchaser agrees to purchase from
the  Seller,  all of the  assets of the  Seller  (collectively,  the  "Assets"),
consisting  primarily  of a parcel of  property in  Northern  Saskatchewan.  The
Seller's sale,  conveyance,  assignment and transfer of the Assets shall be free
and clear of all liens, encumbrances, liabilities or obligations.

     2. Purchase  Price. In full  consideration  for the purchase of the Assets,
the  Purchaser  will issue to the  owners of Seller an  aggregate  of  6,000,000
shares of Purchaser's Common Stock, or 300,000 shares per Syndicate Unit.

     3. Consent of Seller's Owners. All holders of Syndicate Units of the Seller
will execute a Subscription Agreement and Investment Letter in the form provided
by the Purchaser. The Subscription Agreement and Investment Letter will evidence
the consent of each Unit holder to this Agreement.

     4. Governing Law. The  interpretation  and  construction of this Agreement,
and all matters relating  hereto,  shall be governed by the internal laws of the
State of Colorado.

<PAGE>

     IN WITNESS  WHEREOF,  the  parties  hereto  have  caused  their names to be
hereunto subscribed, all as of the day and year first above written.

                                    "PURCHASER"

                                    URANIUM POWER CORPORATION

                                    By:   /s/Thornton J. Donaldson
                                         ---------------------------------------
                                         Thornton J. Donaldson, President

                                    "SELLER"

                                    ATHABASCA URANIUM SYNDICATE

                                    By:   /s/Thornton J. Donaldson
                                         ---------------------------------------
                                         Thornton J. Donaldson, Director

                                    By:   /s/William G. Timmins
                                         ---------------------------------------
                                         William G. Timmins, Director

                                       -2-EXHIBIT 10.7
   phelps
   dodge
Corporation of Canada, Limited

17 December, 1999

Thornton Donaldson, President
Uranium Power Corporation
Suite 206 - 475 Howe Street
Vancouver, BC V6C 2B3

Dear: Thornton

       Re: Athabasca Basin Work Commitment

We refer to the Exploration Option and Operating Joint Venture Agreement made as
of December  16, 1998 (the  "Agreement")  between  Phelps Dodge  Corporation  of
Canada,  Limited ("PDC"), as Optionor, and Uranium Power Corporation ("UPC"), as
Optionee,  regarding  the  Athabasca  Basin,  Saskatchewan  properties,  and  in
particular,  to Section 4.1(c) thereof. We also refer to your letter of November
19, 1999. Unless otherwise defined herein, capitalized terms used in this letter
have the meanings given to them in the Agreement.

Section 4.1(c) of the Agreement describes the Option.  In order to
maintain  the Option,  the  Optionee is required,  among other  things,  to have
completed  by  December  31,  1999  the  Initial  Program  and to have  incurred
Expenditures  of $500,000.  PDC hereby agrees to amend section  4.1(c) to delete
"December 31, 1999" and replace it with "May 31, 2000"  provided that UPC spends
the  balance  of the  $500,000  in the amount of  $120,000  on any of the claims
listed on  Schedule A - Part 1 of the  Agreement  other  than the four  Crawford
claims listed therein.

If you are in agreement with the contents of this letter, please sign and return
the  enclosed  duplicate  copy of this  letter to the  writer  at your  earliest
convenience.

Yours truly,

/s/G.R. Cooke
------------------------------------------------
G. R. Cooke, District Geologist Central District

PHELPS DODGE CORPORATION OF CANADA, LIMITED

Accepted and agreed, this 20th day of December, 1999

/s/Thornton J. Donaldson
------------------------------------------------
Uranium Power Corporation, Thornton J. Donaldson

                Suite 223-530 Century St., Winnipeg, Mb., R3H OY4
                     Phone: 204-772-0773 & Fax: 204-774-3304<PAGE>

                                                                   EXHIBIT 10.18

                             Employment Agreement

                                    between

                                Avenue A, Inc.

                                      and

                                   Sumit Sen

                                                  Dated as of September 29, 1999
<PAGE>

                             Employment Agreement

     This Employment Agreement (this "Agreement"), dated as of September 29,
1999, between Avenue A, Inc., a Washington corporation ("Avenue A"), and Sumit
Sen ("Executive").

                             W I T N E S S E T H:
                             - - - - - - - - - -

     WHEREAS, Executive has been serving as Chief Analytics Officer of Avenue A
and Avenue A desires to retain the services of Executive upon the terms and
conditions set forth herein; and

     WHEREAS, Executive is willing to provide services to Avenue A upon the
terms and conditions set forth herein;

                             A G R E E M E N T S:
                             - - - - - - - - - -

     NOW, THEREFORE, for and in consideration of the foregoing premises and for
other good and valuable consideration, the sufficiency and receipt of which are
hereby acknowledged, Avenue A and Executive hereby agree as follows:

1.   EMPLOYMENT

     Avenue A will employ Executive and Executive will accept employment by
Avenue A as the Chief Analytics Officer of Avenue A. During Executive's
employment, Executive shall serve Avenue A faithfully and to the best of his
ability, devoting substantially all his working time, attention and energies to
the business of Avenue A. Executive's status, duties and responsibilities shall
be reasonably commensurate with his title, and he shall perform such duties as
lawfully assigned to Executive. Executive shall not engage in any other business
activity (except the management of personal investments and charitable and civic
activities which in the aggregate do not interfere with the performance of
Executive's duties hereunder) without first obtaining the written consent of
Avenue A's CEO, such consent not to be unreasonably withheld.

2.   COMPENSATION

     During his employment, Avenue A will pay Executive an annual salary of not
less than $175,000 paid semi-monthly. In addition, Executive has been granted a
stock option for the purchase of 300,000 shares of the common stock of Avenue A,
which is subject to four-year vesting and other conditions in accordance with
the terms
<PAGE>

of the option letter agreement evidencing such option and the terms of the
Avenue A, Inc. 1998 Stock Incentive Compensation Plan.

3.   BENEFITS

     Effective the first month following employment, and during the term of his
employment, Executive will be entitled to participate in Avenue A's health care
benefits and 401k Savings Plan. Avenue A will pay reasonable expenses associated
with relocating Executive to Seattle through Relocation Management, Inc.;
provided, however, that should Executive voluntarily terminate his employment
with Avenue A without "good reason" within one year of his first day of
employment, Executive shall reimburse Avenue A for the expenses relating to his
relocation previously paid or reimbursed by Avenue A.

4.   TERMINATION

     Employment of Executive pursuant to this Agreement may be terminated as
follows:

     4.1.  By Avenue A

     With or without Cause (as defined below), Avenue A may terminate the
employment of Executive at any time upon giving Notice of Termination (as
defined below).

     4.2.  By Executive

     Executive may terminate his employment at any time, for any reason, upon
giving Notice of Termination.

     4.3.  Automatic Termination

     This Agreement and Executive's employment hereunder shall terminate
automatically upon the death or total disability of Executive. The term "total
disability" as used herein shall mean Executive's inability to perform the
duties set forth in paragraph 1 hereof for a period or periods aggregating
ninety (90) calendar days in any 12-month period as a result of physical or
mental illness, loss of legal capacity or any other cause beyond Executive's
control, unless Executive is granted a leave of absence by the Board of
Directors of Avenue A. Executive and Avenue A hereby acknowledge that
Executive's ability to perform the duties specified in paragraph 1 hereof is of
the essence of this Agreement. Termination hereunder shall be deemed to be
effective (a) at the end of the calendar month in which Executive's

                                      -2-
<PAGE>

death occurs or (b) immediately upon a determination by the Board of Directors
of Avenue A of Executive's total disability, as defined herein.

     4.4.  Notice

     The term "Notice of Termination" shall mean at least thirty (30) days'
written notice of termination, by either party, of Executive's employment,
during which period Executive's employment and performance of services will
continue; provided, however, that Avenue A may, upon notice to Executive and
without reducing Executive's compensation during such period, excuse Executive
from any or all of his duties during such period. Such a reduction in duties
shall not constitute "good reason" for voluntary termination so as to trigger
termination payments in accordance with subparagraph 5.2. The effective date of
the termination (the "Termination Date") of Executive's employment hereunder
shall be the date on which such 30-day period expires.

5.   TERMINATION PAYMENTS AND ACCELERATION OF VESTING

     In the event of termination of the employment of Executive, all
compensation and benefits set forth in this Agreement shall terminate except as
specifically provided in this paragraph 5:

     5.1.  Termination by Avenue A

     (a) Upon termination by Avenue A, Avenue A shall pay Executive any unpaid
annual base salary which has accrued for services already performed as of the
Termination Date.

     (b) If Avenue A terminates Executive's employment without Cause, as defined
below, Executive shall be entitled to receive termination payments equal to six
(6) months annual base salary, plus an additional three months base salary for
each year in which the Executive has been employed with Avenue A, up to a total
termination benefit of twelve (12) months annual base salary; further provided
that regardless of the length of Executive's employment with Avenue A, should
Executive remain continuously unemployed after his termination from Avenue A, he
shall be entitled to receive severance payments for each month in which he
remains unemployed after termination up to a maximum of 12 months. The
termination payments shall be calculated according to Executive's base salary as
of the date of Notice of Termination and the termination payments will be paid
semi-monthly in equal parts in accordance with the same time schedule that
Avenue A or a Successor Company (as defined in Exhibit A hereto and incorporated
by reference herein) makes

                                      -3-
<PAGE>

its customary payroll. Avenue A or a Successor Company may deduct customary
withholdings including social security, federal and state income taxes, and
state disability insurance from these severance payments; however, any and all
such obligations shall be Executive's responsibility. Avenue A will issue and
file appropriate Form 1099 or similar tax documents in connection with any
termination payments. The termination payments described in this paragraph are
expressly contingent upon Executive's signing upon termination a release in the
form attached hereto as Exhibit B, and are further contingent upon Executive's
full compliance with the terms of his Confidentiality, Inventions Assignment,
Noncompetition and Nonsolicitation Agreement with Avenue A (the "Confidentiality
Agreement"), a copy of which is attached hereto as Exhibit C. In the event
Executive were to materially breach this Confidentiality Agreement, his right to
any termination payments under this paragraph shall be extinguished, Avenue A
(and any Successor Company) shall cease payments, and Executive shall
immediately return to Avenue A or to any Successor Company any severance
payments already made. If Executive is terminated by either of Avenue A or any
Successor Company for Cause, Executive shall not be entitled to receive any of
the foregoing benefits, other than those set forth in clause (a) above.

     (c) If Avenue A terminates Executive's employment without Cause, as defined
below, then (1) the portion of any Avenue A stock option held by Executive
immediately prior to the Termination Date that is unvested shall automatically
vest, immediately prior to the Termination Date, in an amount equal to the
portion that would have vested during the one year period immediately following
the Termination Date (assuming, for purpose of determining the amount, that no
termination had occurred and Executive had continued Executive's employment with
Avenue A during that one year period), and (2) the number of unvested shares, if
any, held by Executive immediately prior to the Termination Date that were
obtained on exercise of any Avenue A stock options that is equal to the number
of such unvested shares that would have vested during the one year period
immediately after the Termination Date (assuming, for purposes of determining
the number, that no termination had occurred and Executive had continued
Executive's employment with Avenue A during that one year period) shall,
immediately prior to the Termination Date, automatically vest and be no longer
subject to the right of repurchase in favor of Avenue A. If the one year
anniversary of the Termination Date falls in the middle of a quarter for option
or share vesting purposes, the vesting acceleration described above shall be pro
rated for the actual number of days between the beginning of such quarter and
the one year anniversary date. Any acceleration of vesting of stock options or
of unvested shares pursuant to the terms of any stock option plan of Avenue A
under which any stock option held by Executive is granted (a "Company Stock
Option Plan") and any acceleration of vesting pursuant to any option letter
agreement for any stock option for Avenue A common stock granted to Executive
prior to or after the date of this

                                      -4-
<PAGE>

Agreement (an "Option Agreement") shall not be limited by or be in lieu of any
acceleration of vesting provided for pursuant to this Agreement, and any
acceleration of vesting provided for pursuant to this Agreement shall not be
limited by or be in lieu of any acceleration of vesting provided for pursuant to
any Company Stock Option Plan or Option Agreement.

     5.2.  Termination by Executive

     In the case of the termination of Executive's employment by Executive for
"good reason," as defined below, Executive shall be entitled to the termination
payments and accelerated vesting benefit as set forth in clauses 5.1(a), (b) and
(c), above. In the case of termination of Executive's employment by Executive
for any other reason, Executive shall not be entitled to any termination
payments or accelerated vesting benefit, other than as set forth in clause
5.1(a), above.

     5.3.  Termination as a Result of Death or Total Disability

     In the event of termination of Executive's employment pursuant to
subparagraph 4.3, Executive or his estate shall be paid the compensation set
forth in clause 5.1(a) and shall not be entitled to any of the benefits under
clauses 5.1(b) or 5.1(c) above.

     5.4.  "Good Reason"

     "Good reason" shall mean the occurrence of any of the following events,
without the consent of the Executive, in connection with or after a "Change of
Control" (as defined in Exhibit A hereto and incorporated by reference herein:

          a) a demotion or other material reduction in the nature or status of
             Executive's responsibilities; provided, however, that a change in
             the person or office to which Executive reports, without a
             corresponding reduction in duties, status and responsibilities,
             shall not constitute "good reason;"

          b) a non-voluntary reduction in the Executive's annual base salary;

          c) requirement by a Successor Company that the Executive relocate his
             principal place of employment to a location that is more than 50
             miles from the principal place of employment where Executive was
             employed immediately prior to the "Change of Control;" or

                                      -5-
<PAGE>

          d) the failure of Avenue A to obtain a satisfactory agreement from any
             Successor Company to assume and perform the obligations under this
             Agreement.

     5.5.  Cause

     Wherever reference is made in this Agreement to termination being with or
without Cause, "Cause" shall include, without limitation, the occurrence of one
or more of the following events:

          (a) willful misconduct, insubordination, or dishonesty in the
     performance of Executive's duties or other knowing and material violation
     of Avenue A's or a Successor Company's policies and procedures in effect
     from time to time which results in a material adverse effect on Avenue A or
     a Successor Company;

          (b) willful actions (or intentional failures to act) in bad faith by
     Executive with respect to Avenue A or a Successor Company that materially
     impair Avenue A's or a Successor Company's business, goodwill or
     reputation;

          (c) conviction of Executive of a felony involving an act of
     dishonesty, moral turpitude, deceit or fraud, or the commission of acts
     that could reasonably be expected to result in such a conviction;

          (d) current use by the Executive of illegal substances; or

          (e) any material violation by Executive of Executive's Confidentiality
     Agreement with Avenue A.

     5.6.  Acceleration in the Event of a Change in Control

     In the event Executive is employed by Avenue A immediately prior to the
date of a "Change in Control" (as defined in Exhibit A hereto and incorporated
by reference herein), then immediately prior to the Change in Control (1) the
number of unvested shares held by Executive at that time that were obtained on
exercise of any Avenue A stock options that is equal to the number of such
unvested shares that would vest during the one year period immediately after the
date of the Change of Control shall automatically vest and be no longer subject
to a right of repurchase in favor of Avenue A and (2) the portion of any Avenue
A stock options held by Executive at that time that is unvested shall
automatically vest in an amount equal to the portion that would vest during the
one year period immediately following the Change of Control, in each of the
cases of (1) and (2) above assuming that Executive's employment had continued
with Avenue A during such one year period. Any

                                      -6-
<PAGE>

acceleration of vesting of stock options or of shares pursuant to the terms of
any stock option plan of Avenue A under which any stock option held by Executive
is granted (a "Company Stock Option Plan") and any acceleration of vesting
pursuant to any option letter agreement for any stock option for Avenue A common
stock granted to Executive prior to or after the date of this Agreement (an
"Option Agreement") shall not be limited by or be in lieu of the acceleration of
vesting provided for pursuant to this Agreement, and any acceleration of vesting
provided for pursuant to this Agreement shall not be limited by or be in lieu of
any acceleration of vesting provided for pursuant to any Company Stock Option
Plan or Option Agreement.

6.   CONFIDENTIALITY, NONCOMPETITION AND NONSOLICITATION AGREEMENT

     Executive is subject to the terms of the Confidentiality Agreement entered
into concurrently with this Agreement and the terms of the Confidentiality
Agreement shall survive the termination of Executive's employment with Avenue A.

7.   REPRESENTATIONS AND WARRANTIES; NO VIOLATION

     In order to induce Avenue A to enter into this Agreement, Executive
represents and warrants to Avenue A that neither the execution nor the
performance of this Agreement by Executive will violate or conflict in any way
with any other agreement by which Executive may be bound, or with any other
duties imposed upon Executive by corporate or other statutory or common law.

8.   NOTICE AND CURE OF BREACH

     Whenever a breach of this Agreement by either party is relied upon as
justification for any action taken by the other party pursuant to any provision
of this Agreement, other than pursuant to the definition of "Cause" set forth in
subparagraph 5.4 hereof, before such action is taken, the party asserting the
breach of this Agreement shall give the other party at least 14 days' prior
written notice of the existence and the nature of such breach before taking
further action hereunder and shall give the party purportedly in breach of this
Agreement the opportunity to correct such breach during the 14-day period.

9.   FORM OF NOTICE

     All notices given hereunder shall be given in writing, shall specifically
refer to this Agreement and shall be personally delivered or sent by telecopy or
other electronic facsimile transmission or by registered or certified mail,
return receipt requested, at the address set forth below or at such other
address as may hereafter be designated by notice given in compliance with the
terms hereof:

                                      -7-
<PAGE>

     If to Executive:    Sumit Sen

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

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

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

     If to Avenue A:     Avenue A, Inc.
                         506 Second Avenue
                         Seattle, WA 98104
                         Facsimile: (206) 521-8808
                         Attention: President and CEO

     Copy to:            Perkins Coie LLP
                         1201 Third Avenue, 48th Floor
                         Seattle, WA 98101-3099
                         Facsimile: (206) 583-8500
                         Attention: James Sanders

If notice is mailed, such notice shall be effective upon mailing, or if notice
is personally delivered or sent by telecopy or other electronic facsimile
transmission, it shall be effective upon receipt.

10.  ASSIGNMENT

     This Agreement is personal to Executive and shall not be assignable by
Executive. Avenue A may assign its rights hereunder to (a) any corporation
resulting from any merger, consolidation or other reorganization to which Avenue
A is a party or (b) any corporation, partnership, association or other person to
which Avenue A may transfer all or substantially all of the assets and business
of Avenue A existing at such time. All of the terms and provisions of this
Agreement shall be binding upon and shall inure to the benefit of and be
enforceable by the parties hereto and their respective successors and permitted
assigns.

11.  WAIVERS

     No delay or failure by any party hereto in exercising, protecting or
enforcing any of its rights, titles, interests or remedies hereunder, and no
course of dealing or performance with respect thereto, shall constitute a waiver
thereof. The express waiver by a party hereto of any right, title, interest or
remedy in a particular instance or circumstance shall not constitute a waiver
thereof in any other instance or circumstance. All rights and remedies shall be
cumulative and not exclusive of any other rights or remedies.

                                      -8-
<PAGE>

12.  ARBITRATION

     Any controversies or claims arising out of or relating to this Agreement
shall be fully and finally settled by arbitration in the city of Seattle,
Washington in accordance with the Commercial Arbitration Rules of the American
Arbitration Association then in effect (the "AAA Rules"), conducted by one
arbitrator either mutually agreed upon by Avenue A and Executive or chosen in
accordance with the AAA Rules, except that the parties thereto shall have any
right to discovery as would be permitted by the Federal Rules of Civil Procedure
for a period of 90 days following the commencement of such arbitration and the
arbitrator thereof shall resolve any dispute which arises in connection with
such discovery. The prevailing party shall be entitled to costs, expenses and
reasonable attorneys' fees, and judgment upon the award rendered by the
arbitrator may be entered in any court having jurisdiction thereof.

13.  AMENDMENTS IN WRITING

     No amendment, modification, waiver, termination or discharge of any
provision of this Agreement, nor consent to any departure therefrom by either
party hereto, shall in any event be effective unless the same shall be in
writing, specifically identifying this Agreement and the provision intended to
be amended, modified, waived, terminated or discharged and signed by Avenue A
and Executive, and each such amendment, modification, waiver, termination or
discharge shall be effective only in the specific instance and for the specific
purpose for which given. No provision of this Agreement shall be varied,
contradicted or explained by any oral agreement, course of dealing or
performance or any other matter not set forth in an agreement in writing and
signed by Avenue A and Executive.

14.  APPLICABLE LAW

     This Agreement shall in all respects, including all matters of
construction, validity and performance, be governed by, and construed and
enforced in accordance with, the laws of the state of Washington, without regard
to any rules governing conflicts of laws.

15.  SEVERABILITY

     If any provision of this Agreement shall be held invalid, illegal or
unenforceable in any jurisdiction, for any reason, including, without
limitation, the duration of such provision, its geographical scope or the extent
of the activities prohibited or required by it, then, to the full extent
permitted by law (a) all other provisions hereof shall remain in full force and
effect in such jurisdiction and shall be liberally construed in order to carry
out the intent of the parties hereto as nearly as may

                                      -9-
<PAGE>

be possible, (b) such invalidity, illegality or unenforceability shall not
affect the validity, legality or enforceability of any other provision hereof,
and (c) any court or arbitrator having jurisdiction thereover shall have the
power to reform such provision to the extent necessary for such provision to be
enforceable under applicable law.

16.  HEADINGS

     All headings used herein are for convenience only and shall not in any way
affect the construction of, or be taken into consideration in interpreting, this
Agreement.

17.  COUNTERPARTS

     This Agreement, and any amendment or modification entered into pursuant to
paragraph 13 hereof, may be executed in any number of counterparts, each of
which counterparts, when so executed and delivered, shall be deemed to be an
original and all of which counterparts, taken together, shall constitute one and
the same instrument.

18.  ENTIRE AGREEMENT

     This Agreement on and as of the date hereof, together with the
Confidentiality Agreement, constitutes the entire agreement between Avenue A and
Executive with respect to the subject matter hereof and all prior or
contemporaneous oral or written communications, understandings or agreements
between Avenue A and Executive with respect to such subject matter are hereby
superseded and nullified in their entireties.

     IN WITNESS WHEREOF, the parties have executed and entered into this
Agreement on the date set forth above.

                                   EXECUTIVE:

                                   Sumit Sen

                                   /s/ Sumit Sen
                                   ---------------------------------------------

                                   AVENUE A:

                                   Avenue A, Inc.

                                   By    /s/ Brian McAndrews
                                     -------------------------------------------
                                     Its President and CEO

                                     -10-
<PAGE>

                                   EXHIBIT A

1.   Definition of "Change of Control"

     For purposes of the Employment Agreement, a "Change of Control" means any
of:

     (i) an event in which any person (including any individual, entity or
group within the meaning of Section 13(d)(3) or 14(d)(2) of the Securities
Exchange Act of 1934, as amended, (the "Exchange Act")) (a "Person"), shall
become the beneficial owner (within the meaning of Rule 13d-3 promulgated under
the Exchange Act), directly or indirectly, of fifty percent (50%) or more of the
combined voting power of the capital stock of Avenue A, Inc. ("Avenue A") then
outstanding; or

     (ii) at any time during which Avenue A has a class of equity securities
which is listed on a national securities exchange or an automated quotation
system (including, without limitation, the Nasdaq Stock Market) ("publicly
traded"), the acquisition by a Person of equity securities representing more
than thirty percent (30%) of the combined voting power of the capital stock of
Avenue A outstanding as of the date of such transaction (or the first of a
series of related transactions), but only if such equity securities were
acquired in a transaction or series of related transactions which were not
approved by the Board of Directors of Avenue A in office prior to the date of
such first acquisition (provided, however that if such Person is entitled,
pursuant to Rule 13d-1 under the Exchange Act to file a Form 13G with respect to
its holdings of equity securities of Avenue A in lieu of a Form 13D, such event
will not constitute a Change of Control unless and until such Person files a
Form 13D with respect to such holdings); or

     (iii) at any time during which Avenue A has a class of equity securities
which is publicly traded, the acquisition by a Person of equity securities
representing more than twenty percent (20%) of the combined voting power of the
capital stock of Avenue A outstanding prior to the date of such transaction (or
the first of a series of related transactions) in a transaction or series of
related transactions which were not approved by the Board of Directors of Avenue
A in office prior to the date of such first acquisition, and, within one year
thereafter, at least two individuals whose election to the Board of Directors
was proposed by such Person are members of the Board of Directors; or

     (iv) the sale or other disposition of all or substantially all of Avenue
A's assets, other than to a corporation with respect to which immediately
following such sale or disposition (A) securities representing more than sixty
percent (60%) of the combined voting power the capital stock of such corporation
are then beneficially owned, directly or indirectly, by all or substantially all
of the beneficial owners of securities representing the combined voting power of
the capital stock of Avenue A (the "Company Voting Securities") immediately
prior to such sale or disposition in substantially the same proportion as their
ownership, immediately prior to such sale or other disposition, of Company
Voting Securities, (B) no Person (excluding Avenue A, any employee benefit plan
(or related trust) of Avenue A or such corporation and any Person beneficially
owning, immediately prior to such sale or other disposition, directly or
indirectly, securities representing 33% or more of Company Voting Securities)
beneficially owns, directly or indirectly, securities representing 33% or more
of the combined voting power of the capital stock of such corporation; and (C)
at least a majority of the members of the board of directors of the such
corporation were approved by majority of directors of the Incumbent Directors
(as defined in subsection (vii))on Avenue A's Board of Directors at the time
such transaction was initially approved by Avenue A.
<PAGE>

     (v) the reorganization, merger or consolidation of Avenue A with any other
corporation or entity, in each case unless immediately following such
reorganization, merger or consolidation (A) securities representing more than
60% of the combined voting power of the capital stock of the corporation
resulting from such reorganization, merger or consolidation are then
beneficially owned, directly, or indirectly, by all or substantially all of the
individuals and entities who were the beneficial owners of Company Voting
Securities immediately prior to such reorganization, merger or consolidation in
substantially the same proportion as their ownership, immediately prior to such
reorganization, merger or consolidation, of Company Voting Securities, (B) no
Person (excluding Avenue A, any employee benefit plan (or related trust) of
Avenue A or such corporation resulting from such reorganization, merger or
consolidation and any Person beneficially owning, immediately prior to such
reorganization, merger or consolidation, directly or indirectly, securities
representing 33% or more of Company Voting Securities) beneficially owns,
directly or indirectly, securities representing 33% or more of the combined
voting power of the corporation resulting from such reorganization, merger or
consolidation, and (C) at least a majority of the members of the board of
directors of the corporation resulting from such reorganization, merger or
consolidation were the Incumbent Directors at the time that the agreement for
such reorganization, merger or consolidation was initially executed; or

     (vi) the dissolution or liquidation of Avenue A; or

     (vii) a change in the composition of the Board of Directors of Avenue A in
which a majority of the seats (other than vacant seats) on the Board have been
occupied by individuals who were neither (a) nominated by a majority of the
Incumbent Directors nor (b) appointed by directors so nominated.

2.   Definition of "Successor Company"

     For purposes of the Employment Agreement, "Successor Company" shall mean
any of (i) any corporation that acquires all or substantially all of the assets
of Avenue A in a "Change of Control" described in clause (iv) of the definition
of "Change of Control" above or (ii) a successor corporation to Avenue A (or
parent corporation thereof) resulting from a "Change in Control" of Avenue A
described in clause (v) of the definition of "Change of Control" above.

                                      -2-
<PAGE>

                                   EXHIBIT B

                              WAIVER AND RELEASE

     For and in consideration of the severance payments and benefits set out in
the Employment Agreement attached hereto, Executive, on behalf of himself and
his agents, heirs, successors and assigns, expressly waives any claims against
Employer and releases Employer (including its officers, directors, stockholders,
managers, agents and representatives) from any and all claims, demands,
liabilities, damages, obligations, actions or causes of action of any kind,
known or unknown, past or present, arising out of, relating to, or in connection
with Executive's employment, termination of employment, or the holding of any
office with Employer or any other related entity. The claims released by
Executive include, but are not limited to, claims for defamation, libel,
invasion of privacy, intentional or negligent infliction of emotional distress,
wrongful termination, constructive discharge, breach of contract, breach of the
covenant of good faith and fair dealing, breach of fiduciary duty, fraud, or for
violation of any federal, state or other governmental statute or ordinance,
including, without limitation, Title VII of the Civil Rights Act of 1964, the
federal Age Discrimination in Employment Act, the Americans with Disabilities
Act, the Family and Medical Leave Act, the Employment Retirement Income Security
Program or any other legal limitation on the employment relationship.

     This waiver and release shall not waive or release claims where the events
in dispute first arise after execution of this Release.

     Executive agrees he has been provided the opportunity to consider for
twenty-one (21) days whether to enter into this Release, and has voluntarily
chosen to enter into it on this date. Executive may revoke this Release for a
period of seven (7) days following the execution of this Release; this Release
shall become effective following expiration of this seven (7) day period. This
Release shall be effective when signed. Executive acknowledges that he is
voluntarily executing this Release, that he has carefully read and fully
understands all aspects of this Release and the attached Employment Agreement,
that he has not relied upon any representations or statements not set forth
herein or made by Avenue A's agents or representatives, that he has been advised
to consult with an attorney prior to executing the Release, and that, in fact,
he has consulted with an attorney of his choice as to the subject matter and
effect of this Release.

---------------------                   ----------------------------------------
Date                                    Sumit Sen
<PAGE>

                                   EXHIBIT C

                           CONFIDENTIALITY AGREEMENT

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