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                                                                       EXHIBIT A
 
                             ON-SITE SOURCING, INC.
                             1998 STOCK OPTION PLAN
 
    1. PURPOSE.
 
    This 1998 Stock Option Plan (the "Plan") is intended to encourage stock
ownership by employees and directors of On-Site Sourcing, Inc. (the "Company"),
a Delaware corporation, its divisions and Subsidiary Corporations, so that they
may acquire or increase their proprietary interest in the Company, and to
encourage such employees and directors to remain in the employ of the Company
and to put forth maximum efforts for the success of the business. It is further
intended that options granted by the Board of Directors of the Company (the
"Board") pursuant to Section 5 hereof shall constitute "incentive stock options"
("Incentive Stock Options") within the meaning of Section 422 of the Internal
Revenue Code of 1986, as amended (the "Code"), and the regulations issued
thereunder, and options granted by the Board pursuant to Section 6 hereof shall
constitute "nonqualified stock options" ("Nonqualified Stock Options") and,
together with Incentive Stock Options ("Options").
 
    2. ADMINISTRATION AND AUTHORITY.
 
    The Plan shall be administered by the Board. The Board shall have the
authority in its discretion, subject to and not inconsistent with the express
provisions of the Plan, to administer the Plan and to exercise all the powers
and authorities either specifically granted to it under the Plan or necessary or
advisable in the administration of the Plan, including, without limitation, the
authority to grant Options; to determine which Options shall constitute
Incentive Stock Options and which Options shall constitute Nonqualified Stock
Options; to determine the purchase price of the shares of Common Stock covered
by each Option (the "Option Price"); to determine the persons to whom, and the
time or times at which, Options shall be granted; to determine the number of
shares of Common Stock to be covered by each Option; to interpret the Plan; to
prescribe, amend and rescind rules and regulations relating to the Plan; to
determine the terms and provisions of the Option Agreements (which need not be
identical) evidencing Options granted under the Plan; and to make all other
determinations deemed necessary or advisable for the administration of the Plan.
The Board may delegate some or all of the powers granted to it pursuant to this
Section 2 to a committee (the "Committee") appointed by the Board and consisting
of not less than two (2) members of the Board. The Board may from time to time
remove members from, or add members to, the Committee, and vacancies on the
Committee shall be filled by the Board. All decisions, determinations and
interpretations of the Committee shall be final and binding on all Optionees,
unless otherwise determined by the Board.
 
    2.2 LIABILITY.
 
    No member of the Board or Committee shall be liable for any action taken or
determination made in good faith with respect to the Plan or any Option.
 
    3. ELIGIBILITY.
 
    Options may be granted to employees (including, without limitation, officers
and directors who are employees of the Company or its present or future
divisions and Subsidiary Corporations). In determining the persons to whom
Options shall be granted and the number of shares to be covered by each Option,
the Board shall take into account the duties of the respective persons, their
present and potential contributions to the success of the Company and such other
factors as the Board shall deem relevant in connection with accomplishing the
purpose of the Plan. A person to whom an Option has been granted is sometimes
 
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referred to herein as an "Optionee." An Optionee shall be eligible to receive
more than one Option during the term of the Plan, but only on the terms and
subject to the restrictions hereinafter set forth.
 
    4. SHARES.
 
    The shares subject to Options hereunder shall be shares of the Company's
Common Stock (the "Common Stock"). Such shares may, in whole or in part, be
authorized but unissued shares or shares that shall have been or that may be
reacquired by the Company. The aggregate number of shares of Common Stock as to
which Options may be granted from time to time under the Plan shall not exceed
700,000, all of which may be in the form of either Incentive Stock Options or
Nonqualified Stock Options. The aggregate number of shares of Common Stock as to
which Options may be granted under the Plan to an individual in any calendar
year shall not exceed 350,000. If any Option expires, is canceled, or terminates
for any other reason, the shares of Common Stock available under that Option
will again be available for the granting of new options (but will be counted
against that calendar year's limit for a given individual). The limitation
established by this Section shall be subject to adjustment as provided in
Section 7.9 hereof. If any outstanding Option expires or is terminated without
having been exercised in full, the shares of Common Stock allocable to the
unexercised portion of such Option shall (unless the Plan shall have been
terminated) become available for subsequent grants of Options.
 
    5. INCENTIVE STOCK OPTIONS.
 
    Options granted pursuant to this Section 5 are intended to constitute
Incentive Stock Options and shall be subject to the following special terms and
conditions, in addition to the general terms and conditions specified in Section
7 hereof.
 
    5.1 VALUE OF SHARES.
 
    The aggregate Fair Market Value (determined as of the date the Incentive
Stock Option is granted) of the shares of Common Stock with respect to which
Options granted under this Plan and all other option plans of the Company and
any Subsidiary Corporation become exercisable for the first time by an Optionee
during any calendar year shall not exceed $100,000.
 
    5.2 TEN PERCENT STOCKHOLDER.
 
    In the case of an Incentive Stock Option granted to a Ten Percent
Stockholder, (a) the Option Price shall not be less than 110% of the Fair Market
Value of the shares of Common Stock of the Company on the date of grant of such
Incentive Stock Option, and (b) the exercise period shall not exceed five (5)
years from the date of grant of such Incentive Stock Option.
 
    6. NONQUALIFIED STOCK OPTIONS.
 
    Options granted pursuant to this Section 6 are intended to constitute
Nonqualified Stock Options and shall be subject only to the general terms and
conditions specified in Section 7 hereof.
 
    7. TERMS AND CONDITIONS OF OPTIONS.
 
    Each Option shall be evidenced by a written Option Agreement between the
Company and the Optionee, which agreement shall comply with and be subject to
the following terms and conditions:
 
    7.1 NUMBER OF SHARES.
 
    Each Option Agreement shall state the number of shares of Common Stock to
which the Option relates.
 
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    7.2 TYPE OF OPTION.
 
    Each Option Agreement shall specifically identify the portion, if any, of
the Option which constitutes an Incentive Stock Option and the portion, if any,
which constitutes a Nonqualified Stock Option.
 
    7.3 OPTION PRICE.
 
    Each Option Agreement shall state the Option Price which, in the case of
Incentive Stock Options, shall be not less than 100% of the Fair Market Value of
the shares of Common Stock of the Company on the date of grant of the Option.
The Option Price shall be subject to adjustment as provided in Section 7.9
hereof. The date as of which the Committee adopts a resolution expressly
granting an Option shall be considered the day on which such Option is granted,
unless the resolution specifies otherwise.
 
    7.4 MEDIUM AND TIME OF PAYMENT.
 
    The Option Price shall be paid in full, at the time of exercise, as the
Committee provides in the Option Agreement, initially or by amendment. Payment
shall be in cash, or in shares of Common Stock having a Fair Market Value equal
to such Option Price, or in a combination of cash and such shares, or by such
other method as the Committee permits. The Optionee may engage in a cashless
exercise using a broker to pay the exercise price. The Committee may restrict
the use of Common Stock as a payment method. The exercise may be effected in
whole or in part (a) with monies received from the Company at the time of
exercise as a compensatory cash payment, or (b) with monies borrowed from the
Company pursuant to repayment terms and conditions as shall be determined from
time to time by the Board, in its discretion separately with respect to each
exercise of Options and each Optionee; provided, however, that each such method
and time for payment and each such borrowing and terms and conditions of
repayment shall be permitted by and be in compliance with applicable law, and
provided, further, if the Option Price is paid with monies borrowed from the
Company, such fact shall be noted conspicuously on the certificate evidencing
such shares in accordance with applicable law.
 
    7.5 TERM AND EXERCISE OF OPTIONS.
 
    Options shall be exercisable over the exercise period as and at the times
and upon the conditions that the Board may determine, as reflected in the Option
Agreement; provided, however, that the Board shall have the authority to
accelerate the exercisability of any outstanding Option at such time and under
such circumstances as it, in its sole discretion, deems appropriate. The
exercise period shall be determined by the Board for all Options; provided,
however that such exercise period shall not exceed ten (10) years from the date
of grant of such Option. The exercise period shall be subject to earlier
termination as provided in Sections 7.6 and 7.7 hereof. An Option may be
exercised, as to any or all full shares of Common Stock as to which the Option
has become exercisable, by giving written notice of such exercise to the Board;
provided, however, that an Option may not be exercised at any one time as to
fewer than 100 shares (or such number of shares as to which the Option is then
exercisable if such number of shares is less than 100).
 
    7.6 TERMINATION.
 
    Except as provided in Section 7.5 and in this Section 7.6 hereof, an Option
may not be exercised unless the Optionee is then in the employ of the Company or
a division or Subsidiary Corporation (or a corporation issuing or assuming the
Option in a transaction to which IRC Section 425(a) of the Code applies), and
unless the Optionee has remained continuously so employed since the date of
grant of the Option. If the employment of an Optionee shall terminate (other
than by reason of death, disability or retirement), all Options of such Optionee
that are exercisable at the time of such termination may, unless earlier
terminated in accordance with their terms, be exercised within three months
after such termination; provided, however, that if the employment of an Optionee
shall terminate for cause, all Options theretofore granted to such Optionee
shall, to the extent not theretofore exercised, terminate forthwith.
 
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Nothing in the Plan or in any Option shall confer upon an individual any right
to continue in the employ of the Company or any of its divisions or Subsidiary
Corporations or interfere in any way with the right of the Company or any such
division or Subsidiary Corporation to terminate such employment.
 
    7.7 DEATH, DISABILITY OR RETIREMENT.
 
    If an Optionee shall die while employed by the Company, or a Subsidiary
Corporation thereof, or within three months after the termination of such
Optionee's employment, other than for cause, or if the Optionee's employment
shall terminate by reason of disability or retirement, all Options theretofore
granted to such Optionee (to the extent otherwise exercisable) may, unless
earlier terminated in accordance with their terms, be exercised by the Optionee
or by the Optionee's estate or by a person who acquired the right to exercise
such Option by bequest or inheritance or otherwise by reason of the death or
disability of the Optionee, at any time within one year after the date of death,
disability or retirement of the Optionee.
 
    7.8 NONTRANSFERABILITY OF OPTIONS.
 
    Options granted under the Plan shall not be transferable otherwise than (a)
by will; (b) by the laws of descent and distribution; or (c) to a revocable
inter vivos trust for the primary benefit of the Optionee and his or her spouse.
Options may be exercised, during the lifetime of the Optionee, only by the
Optionee, his or her guardian, legal representative or the Trustee of an above
described trust.
 
    7.9 EFFECT OF CERTAIN CHANGES.
 
           (1)  If there is any change in the number of shares of Common Stock
       through the declaration of stock dividends, or through recapitalization
       resulting in stock splits, or combinations or exchanges of such shares,
       the number of shares of Common Stock available for Options, the number of
       such shares covered by outstanding Options and the price per share of
       such Options shall be proportionately adjusted by the Board to reflect
       any increase or decrease in the number of issued shares of Common Stock;
       provided, however, that any fractional shares resulting from such
       adjustment shall be eliminated.
 
           (2)  In the event of the proposed dissolution or liquidation of the
       Company, in the event of any corporate separation or division, including,
       but not limited to, split-up, split-off or spin-off, or in the event of a
       merger or consolidation of the Company with another corporation, the
       Board may provide that the holder of each Option then exercisable shall
       have the right to exercise such Option (at its then Option Price) solely
       for the kind and amount of shares of stock and other securities,
       property, cash or any combination thereof receivable upon such
       dissolution, liquidation, or corporate separation or division, or merger
       or consolidation by a holder of the number of shares of Common Stock for
       which such Option might have been exercised immediately prior to such
       dissolution, liquidation, or corporate separation or division, or merger
       or consolidation; or the Board may provide, in the alternative, that each
       Option granted under the Plan shall terminate as of a date to be fixed by
       the Board; provided, however, that not less than 30 days' written notice
       of the date so fixed shall be given to each Optionee, who shall have the
       right, during the period of 30 days preceding such termination, to
       exercise the Options as to all or any part of the shares of Common Stock
       covered thereby, including shares as to which such Options would not
       otherwise be exercisable; provided, further, that failure to provide such
       notice shall not invalidate or affect the action with respect to which
       such notice was required.
 
           (3)  If while unexercised Options remain outstanding under the Plan,
       the stockholders of the Company approve a definitive agreement to merge
       or consolidate the Company with or into another corporation or to sell or
       otherwise dispose of all or substantially all of its assets, or adopt a
       plan of liquidation (each, a "Disposition Transaction"), then the Board
       may (a) make an
 
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       appropriate adjustment to the number and class of shares available for
       Options, and to the amount and kind of shares or other securities or
       property (including cash) receivable upon exercise of any outstanding
       Options after the effective date of such transaction, and the price
       thereof, or, in lieu of such adjustment, provide for the cancellation of
       all Options outstanding at or prior to the effective date of such
       transaction; (b) provide that exercisability of all Options shall be
       accelerated, whether or not otherwise exercisable; or (c) in its
       discretion, permit Optionees to surrender outstanding Options for
       cancellation; provided, however, that if the stockholders approve such
       Disposition Transaction within five years of the date of adoption of this
       Plan, the Board shall provide for the alternative in (b) above. Upon any
       cancellation of an outstanding Option pursuant to this Section, the
       Optionee shall be entitled to receive, in exchange therefore a cash
       payment under any such Option in an amount per share determined by the
       Board in its sole discretion, but not less than the difference between
       the per share exercise price of such Option and the Fair Market Value of
       a share of the Company Common Stock on such date as the Board shall
       determine.
 
           (4)  Paragraphs (2) and (3) of this Section 7.9 shall not apply to a
       merger or consolidation in which the Company is the surviving corporation
       and shares of Common Stock are not converted into or exchanged for stock,
       securities of any other corporation, cash or any other thing of value.
       Notwithstanding the preceding sentence, in case of any consolidation or
       merger of another corporation into the Company in which the Company is
       the surviving corporation and in which there is a reclassification or
       change (including a change to the right to receive cash or other
       property) of the shares of Common Stock (other than a change in par
       value, or from par value to no par value, or as a result of a subdivision
       or combination, but including any change in such shares into two or more
       classes or series of shares), the Board may provide that the holder of
       each Option then exercisable shall have the right to exercise such Option
       solely for the kind and amount of shares of stock and other securities
       (including those of any new direct or indirect parent of the Company),
       property, cash or any combination thereof receivable upon such
       reclassification, change, consolidation or merger by the holder of the
       number of shares of Common Stock for which such Option might have been
       exercised.
 
           (5)  In the event of a change in the Common Stock of the Company as
       presently constituted which is limited to a change of all, of its
       authorized shares with par value into the same number of shares with a
       different par value or without par value, the shares resulting from any
       such change shall be deemed to be the Common Stock within the meaning of
       the Plan.
 
           (6)  To the extent that the foregoing adjustments relate to stock or
       securities of the Company, such adjustments shall be made by the Board,
       whose determination in that respect shall be final, binding and
       conclusive, provided that each Incentive Stock Option granted pursuant to
       this Plan shall not be adjusted in a manner that causes such Option to
       fail to continue to qualify as an Incentive Stock Option within the
       meaning of Section 422 of the Code.
 
           (7)  Except as otherwise expressly provided in this Section 7.9, the
       Optionee shall have no rights by reason of any subdivision or
       consolidation of shares of stock or any class or the payment of any stock
       dividend or any other increase or decrease in the number of shares of
       stock of any class or by reason of any dissolution, liquidation, merger,
       or consolidation or spin-off of assets or stock of another corporation;
       and any issuance by the Company of shares of stock of any class shall not
       affect, and no adjustment by reason thereof shall be made with respect
       to, the number or price of shares of Common Stock subject to the Option.
       The grant of an Option pursuant to the Plan shall not affect in any way
       the right or power of the Company to make adjustments, reclassifications,
       reorganizations or changes of its capital or business structures or to
       merge or to consolidate or to dissolve, liquidate or sell, or transfer
       all or part of its business or assets.
 
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    7.10 RIGHTS AS A STOCKHOLDER.
 
    An Optionee or an allowable transferee of an Option shall have no rights as
a stockholder with respect to any shares covered by the Option until the date of
the issuance of a certificate evidencing such shares. No adjustment shall be
made for dividends (ordinary or extraordinary, whether in cash, securities or
other property) or distribution of other rights for which the record date is
prior to the date such certificate is issued, except as provided in Section 7.9
hereof.
 
    7.11 OTHER PROVISIONS.
 
    The Option Agreements authorized under the Plan shall contain such other
provisions, including, without limitation, (a) the imposition of restrictions
upon the exercise of an Option; (b) in the case of an Incentive Stock Option,
the inclusion of any condition not inconsistent with such Option qualifying as
an Incentive Stock Option; and (c) conditions relating to compliance with
applicable federal and state securities laws, as the Board shall deem advisable.
 
    8. AGREEMENT BY OPTIONEE REGARDING WITHHOLDING TAXES.
 
    As a condition to the exercise, each Optionee shall agree that (a) no later
than the date of exercise of any Option, the Optionee will pay to the Company or
make arrangements satisfactory to the Board regarding payment of any federal,
state or local taxes of any kind required by law to be withheld upon the
exercise of such Option, and (b) the Company shall, to the extent permitted or
required by law, have the right to deduct federal, state and local taxes of any
kind required by law to be withheld upon the exercise of such Option from any
payment of any kind otherwise due to the Optionee.
 
    9. TERM OF PLAN.
 
    Options may be granted pursuant to the Plan from time to time within a
period of ten (10) years from the date the Plan is adopted by the Board, or the
date the Plan is approved by the stockholders of the Company, whichever is
earlier.
 
    10. DEFINITIONS.
 
    As used in this Plan, the following words and phrases shall have the
meanings indicated:
 
        (a)  "DISABILITY" shall mean an Optionee's inability to engage in any
    substantial gainful activity by reason of any medically determinable
    physical or mental impairment that can be expected to result in death or
    that has lasted or can be expected to last for a continuous period of not
    less than one year.
 
        (b)  "FAIR MARKET VALUE" per share as of a particular date shall mean
    (i) the closing sales price per share of Common Stock on a national
    securities exchange for the last preceding date on which there was a sale of
    such Common Stock on such exchange; or (ii) if the shares of Common Stock
    are then traded on an over-the-counter market, the average of the closing
    bid and ask prices for the shares of Common Stock in such over-the-counter
    market for the last preceding date on which there was a sale of such Common
    Stock on such market; or (iii) in case no reported sale takes place, the
    average of the closing bid and ask prices on the National Association of
    Securities Dealers' Automated Quotations System ("NASDAQ") or any comparable
    system, or if the shares of Common Stock are not listed on NASDAQ or a
    comparable system, the closing sale price or, in case no reported sale takes
    place, the average of the closing bid and asked prices, as furnished by any
    member of the National Association of Securities Dealers, Inc. selected from
    time to time by the Company for that purpose; or (iv) if the shares of
    Common Stock are not then listed on a national securities exchange or traded
    in an over-the-counter market, such value as the Board in its discretion may
    determine.
 
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        (c)  "PARENT COMPANY" shall mean any corporation (other than the
    Company) in an unbroken chain of corporations ending with the employer
    corporation if, at the time of granting an Option, each of the corporations
    other than the employer corporation owns stock possessing 50% or more of the
    total combined voting power of all classes of stock in one of the other
    corporations in such chain.
 
        (d)  "RETIREMENT" shall mean an Optionee's termination of employment for
    any reason at or after age 65.
 
        (e)  "SUBSIDIARY CORPORATION" shall mean any corporation (other than the
    Company) in an unbroken chain of corporations beginning with the employer
    corporation if, at the time of granting an Option, each of the corporations
    other than the last corporation in the unbroken chain owns stock possessing
    50% or more of the total combined voting power of all classes of stock in
    one of the other corporations in such chain.
 
        (f)  "TEN PERCENT STOCKHOLDER" shall mean an Optionee who, at the time
    an Incentive Stock Option is granted, owns stock possessing more than 10% of
    the total combined voting power of all classes of stock of the Company or of
    its Parent or Subsidiary Corporations.
 
    11. AMENDMENT AND TERMINATION OF THE PLAN.
 
    The Board at any time and from time to time may suspend, terminate, modify
or amend the Plan; provided, however, that, to the extent necessary to preserve
Incentive Stock Option treatment or comply with regulatory requirements, any
such amendment shall be subject to the approval of the holders of a majority of
the Common Stock issued and outstanding. Except as provided in Section 7 hereof,
no suspension, termination, modification or amendment of the Plan may adversely
affect any Option previously granted, unless the written consent of the Optionee
is obtained.
 
    12. APPROVAL OF STOCKHOLDERS.
 
    The Plan shall take effect upon its adoption by the Board of Directors but
shall be subject to the approval of the holders of a majority of the issued and
outstanding shares of Common Stock of the Company, which approval must occur
within twelve (12) months after the date the Plan is adopted by the Board.
 
    13. EFFECT OF HEADINGS.
 
    The section and subsection headings contained herein are for convenience
only and shall not affect the construction hereof.
 
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