<Page>

                                                                     EXHIBIT 4.5

THE REGISTERED HOLDER OF THIS PURCHASE OPTION BY ITS ACCEPTANCE HEREOF, AGREES
THAT IT WILL NOT SELL, TRANSFER OR ASSIGN THIS PURCHASE OPTION EXCEPT AS HEREIN
PROVIDED AND THE REGISTERED HOLDER OF THIS PURCHASE OPTION AGREES THAT IT WILL
NOT SELL, TRANSFER, ASSIGN, PLEDGE OR HYPOTHECATE THIS PURCHASE OPTION FOR A
PERIOD OF ONE YEAR FOLLOWING THE EFFECTIVE DATE (DEFINED BELOW) TO ANYONE OTHER
THAN (I) FERRIS, BAKER WATTS, INCORPORATED ("FBW") OR AN UNDERWRITER OR A
SELECTED DEALER IN CONNECTION WITH THE OFFERING, OR (II) A BONA FIDE OFFICER OR
PARTNER OF FBW OR OF ANY SUCH UNDERWRITER OR SELECTED DEALER.

THIS PURCHASE OPTION IS NOT EXERCISABLE PRIOR TO THE LATER OF THE CONSUMMATION
BY HARBOR ACQUISITION CORPORATION ("COMPANY") OF A MERGER, CAPITAL STOCK
EXCHANGE, ASSET ACQUISITION OR OTHER SIMILAR BUSINESS COMBINATION ("BUSINESS
COMBINATION") (AS DESCRIBED MORE FULLY IN THE COMPANY'S REGISTRATION STATEMENT
(DEFINED HEREIN)) OR                     , 2007. VOID AFTER 5:00 P.M. NEW YORK
CITY LOCAL TIME,              ;______________, 2011.

                          FORM OF UNIT PURCHASE OPTION

                               FOR THE PURCHASE OF

                                  500,000 UNITS

                                       OF

                         HARBOR ACQUISITION CORPORATION

1.   PURCHASE OPTION.

       THIS CERTIFIES THAT, in consideration of $100.00 duly paid by or on
behalf of Ferris, Baker Watts, Incorporated ("HOLDER"), as registered owner of
this Purchase Option, to Harbor Acquisition Corporation ("COMPANY"), Holder is
entitled, at any time or from time to time upon the later of the consummation of
a Business Combination or             , 2007 ("COMMENCEMENT DATE"), and at or
before 5:00 p.m., New York City local time, __________________, 2011
("EXPIRATION DATE"), but not thereafter, to subscribe for, purchase and receive,
in whole or in part, up to Five Hundred Thousand (500,000) units ("UNITS") of
the Company, each Unit consisting of one share of common stock of the Company,
par value $0.0001 per share ("COMMON STOCK"), and two warrants ("WARRANT(s)")
expiring five years from the effective date ("EFFECTIVE DATE") of the
registration statement ("REGISTRATION STATEMENT") pursuant to which Units are
offered for sale to the public ("OFFERING"). Each Warrant is the same as the
warrants included in the Units being registered for sale to the public by way of
the Registration Statement ("PUBLIC WARRANTS"), except that the Warrants shall
have an exercise price of $6.25 per whole share, subject to adjustment as
provided in Section 4 of the Warrant Agreement and shall be entitled to cashless
exercise rights as provided in Section 3.4 thereof. If the Expiration Date is a
day on which banking institutions are authorized by law to close, then this
Purchase Option may be exercised on the next succeeding day which is not such a
day in accordance with the terms herein. During the period ending on the
Expiration Date, the Company agrees not to take any action that would terminate
the Purchase Option. This Purchase Option is initially exercisable at $7.50 per
Unit so purchased; provided, however, that upon the occurrence of any of the
events specified in Section 6 hereof, the rights granted by this Purchase
Option, including the exercise price per Unit and the number of Units (and
shares of Common Stock and Warrants) to be received upon such exercise, shall be
adjusted as therein specified. The term "EXERCISE PRICE" shall mean the initial
exercise price or the adjusted exercise price, depending on the context.

                                        1
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2.   EXERCISE.

     2.1  EXERCISE FORM. In order to exercise this Purchase Option, the exercise
form attached hereto as EXHIBIT A must be duly executed and completed and
delivered to the Company, together with this Purchase Option and payment of the
Exercise Price for the Units being purchased payable in cash or by certified
check or official bank check. If the subscription rights represented hereby
shall not be exercised at or before 5:00 p.m., New York City local time, on the
Expiration Date this Purchase Option shall become and be void without further
force or effect, and all rights represented hereby shall cease and expire.

3.   TRANSFER.

     3.1  GENERAL RESTRICTIONS. The registered Holder of this Purchase Option,
by its acceptance hereof, agrees that it will not sell, transfer, assign, pledge
or hypothecate this Purchase Option for a period of one year following the
Effective Date to anyone other than (i) FBW or an underwriter or a selected
dealer in connection with the Offering, or (ii) a bona fide officer or partner
of FBW or of any such underwriter or selected dealer. On and after the first
anniversary of the Effective Date, transfers to others may be made subject to
compliance with or exemptions from applicable securities laws. In order to make
any permitted assignment, the Holder must deliver to the Company the assignment
form attached hereto as EXHIBIT B duly executed and completed, together with the
Purchase Option and payment of all transfer taxes, if any, payable in connection
therewith. The Company shall within five business days transfer this Purchase
Option on the books of the Company and shall execute and deliver a new Purchase
Option or Purchase Options of like tenor to the appropriate assignee(s)
expressly evidencing the right to purchase the aggregate number of Units
purchasable hereunder or such portion of such number as shall be contemplated by
any such assignment.

     3.2  RESTRICTIONS IMPOSED BY THE ACT. The securities evidenced by this
Purchase Option shall not be transferred unless and until (i) the Company has
received the opinion of counsel for the Holder that the securities may be
transferred pursuant to an exemption from registration under the Act and
applicable state securities laws, the availability of which is established to
the reasonable satisfaction of the Company (the Company hereby agreeing that the
opinion of Davis, Malm & D'Agostine, P.C. shall be deemed satisfactory evidence
of the availability of an exemption), or (ii) a registration statement or a
post-effective amendment to the Registration Statement relating to such
securities has been filed by the Company and declared effective by the
Securities and Exchange Commission (the "COMMISSION") and compliance with
applicable state securities law has been established.

4.   NEW PURCHASE OPTIONS TO BE ISSUED.

     4.1  PARTIAL EXERCISE OR TRANSFER. Subject to the restrictions in Section
3 hereof, this Purchase Option may be exercised or assigned in whole or in part.
In the event of the exercise or assignment hereof in part only, upon surrender
of this Purchase Option for cancellation, together with the duly executed
exercise or assignment form and funds sufficient to pay any Exercise Price
and/or transfer tax, the Company shall cause to be delivered to the Holder
without charge a new Purchase Option of like tenor to this Purchase Option in
the name of the Holder evidencing the right of the Holder to purchase the number
of Units purchasable hereunder as to which this Purchase Option has not been
exercised or assigned.

     4.2  LOST CERTIFICATE. Upon receipt by the Company of evidence satisfactory
to it of the loss, theft, destruction or mutilation of this Purchase Option and
of reasonably satisfactory indemnification or the posting of a bond, the Company
shall execute and deliver a new Purchase Option of like tenor and date. Any such
new Purchase Option executed and delivered as a result of such loss, theft,
mutilation or destruction shall constitute a substitute contractual obligation
on the part of the Company.

5.   INTENTIONALLY OMITTED.

                                        2
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6.   ADJUSTMENTS.

     6.1  ADJUSTMENTS TO EXERCISE PRICE AND NUMBER OF SECURITIES. The Exercise
Price and the number of Units underlying the Purchase Option shall be subject to
adjustment from time to time as hereinafter set forth:

          6.1.1  STOCK DIVIDENDS - SPLIT-UPS. If after the date hereof, and
subject to the provisions of Section 6.4 below, the number of outstanding shares
of Common Stock is increased by a stock dividend payable in shares of Common
Stock or by a split-up of shares of Common Stock or other similar event, then,
on the effective date thereof, the number of shares of Common Stock underlying
each of the Units purchasable hereunder shall be increased in proportion to such
increase in outstanding shares. In such case, the number of shares of Common
Stock, and the exercise price applicable thereto, underlying the Warrants
underlying each of the Units purchasable hereunder shall be adjusted in
accordance with the terms of the Warrants. For example, if the Company declares
a two-for-one stock dividend and at the time of such dividend this Purchase
Option is for the purchase of one Unit at $7.50 per whole Unit (each Warrant
underlying the Units is exercisable for $6.25 per share), upon effectiveness of
the dividend, this Purchase Option will be adjusted to allow for the purchase of
one Unit at $7.50 per Unit, each Unit entitling the holder to receive two shares
of Common Stock and four Warrants (each Warrant exercisable for $3.125 per
share).

          6.1.2  AGGREGATION OF SHARES. If after the date hereof, and subject to
the provisions of Section 6.4, the number of outstanding shares of Common Stock
is decreased by a consolidation, combination or reclassification of shares of
Common Stock or other similar event, then, on the effective date thereof, the
number of shares of Common Stock underlying each of the Units purchasable
hereunder shall be decreased in proportion to such decrease in outstanding
shares. In such case, the number of shares of Common Stock, and the exercise
price applicable thereto, underlying the Warrants underlying each of the Units
purchasable hereunder shall be adjusted in accordance with the terms of the
Warrants.

          6.1.3  REPLACEMENT OF SECURITIES UPON REORGANIZATION, ETC. In case of
any reclassification or reorganization of the outstanding shares of Common Stock
other than a change covered by Section 6.1.1 or 6.1.2 hereof or that solely
affects the par value of such shares of Common Stock, or in the case of any
merger or consolidation of the Company with or into another corporation (other
than a consolidation or merger in which the Company is the continuing
corporation and that does not result in any reclassification or reorganization
of the outstanding shares of Common Stock), or in the case of any sale or
conveyance to another corporation or entity of the property of the Company as an
entirety or substantially as an entirety in connection with which the Company is
dissolved, the Holder of this Purchase Option shall have the right thereafter
(until the expiration of the right of exercise of this Purchase Option) to
receive upon the exercise hereof, for the same aggregate Exercise Price payable
hereunder immediately prior to such event, the kind and amount of shares of
stock or other securities or property (including cash) receivable upon such
reclassification, reorganization, merger or consolidation, or upon a dissolution
following any such sale or transfer, by a Holder of the number of shares of
Common Stock of the Company obtainable upon exercise of this Purchase Option and
the underlying Warrants immediately prior to such event; and if any
reclassification also results in a change in shares of Common Stock covered by
Section 6.1.1 or 6.1.2, then such adjustment shall be made pursuant to Sections
6.1.1, 6.1.2 and this Section 6.1.3. The provisions of this Section 6.1.3 shall
similarly apply to successive reclassifications, reorganizations, mergers or
consolidations, sales or other transfers.

          6.1.4  CHANGES IN FORM OF PURCHASE OPTION. This form of Purchase
Option need not be changed because of any change pursuant to this Section, and
Purchase Options issued after such change may state the same Exercise Price and
the same number of Units as are stated in the Purchase Options initially issued
pursuant to this Agreement. The acceptance by any Holder of the issuance of new
Purchase Options reflecting a required or permissive change shall not be deemed
to waive any rights to an adjustment occurring after the Commencement Date or
the computation thereof.

     6.2  SUBSTITUTE PURCHASE OPTION. In case of any consolidation of the
Company with, or merger of the Company with, or merger of the Company into,
another corporation (other than a consolidation or merger which does not result
in any reclassification or change of the outstanding Common Stock), the
corporation formed by such consolidation or merger shall execute and deliver to
the Holder a supplemental Purchase Option providing that the holder of each
Purchase Option then outstanding or to be outstanding shall have the right
thereafter (until the stated

                                        3
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expiration of such Purchase Option) to receive, upon exercise of such Purchase
Option, the kind and amount of shares of stock and other securities and property
receivable upon such consolidation or merger, by a holder of the number of
shares of Common Stock of the Company for which such Purchase Option might have
been exercised immediately prior to such consolidation, merger, sale or
transfer. Such supplemental Purchase Option shall provide for adjustments which
shall be identical to the adjustments provided in Section 6. The above provision
of this Section shall similarly apply to successive consolidations or mergers.

     6.3  ELIMINATION OF FRACTIONAL INTERESTS. The Company shall not be required
to issue certificates representing fractions of shares of Common Stock or
Warrants upon the exercise of the Purchase Option, nor shall it be required to
issue scrip or pay cash in lieu of any fractional interests, it being the intent
of the parties that all fractional interests shall be eliminated by rounding any
fraction up to the nearest whole number of Warrants, shares of Common Stock or
other securities, properties or rights.

7.   RESERVATION AND LISTING. The Company shall at all times reserve and keep
available out of its authorized shares of Common Stock, solely for the purpose
of issuance upon exercise of the Purchase Options or the Warrants underlying the
Purchase Option, such number of shares of Common Stock or other securities,
properties or rights as shall be issuable upon the exercise thereof. The Company
covenants and agrees that, upon exercise of the Purchase Options and payment of
the Exercise Price therefor, all shares of Common Stock and other securities
issuable upon such exercise shall be duly and validly issued, fully paid and
non-assessable and not subject to preemptive rights of any stockholder. The
Company further covenants and agrees that upon exercise of the Warrants
underlying the Purchase Options and payment of the respective Warrant exercise
price therefor, all shares of Common Stock and other securities issuable upon
such exercise shall be duly and validly issued, fully paid and non-assessable
and not subject to preemptive rights of any stockholder. As long as the Purchase
Options shall be outstanding, the Company shall use its best efforts to cause
all (i) Units and shares of Common Stock issuable upon exercise of the Purchase
Options, (iii) Warrants issuable upon exercise of the Purchase Options and (iv)
shares of Common Stock issuable upon exercise of the Warrants included in the
Units issuable upon exercise of the Purchase Option to be listed (subject to
official notice of issuance) on all securities exchanges (or, if applicable on
the Nasdaq National Market, SmallCap Market, OTC Bulletin Board or any successor
trading market) on which the Units, the Common Stock or the Public Warrants
issued to the public in connection herewith may then be listed and/or quoted.

8.   CERTAIN NOTICE REQUIREMENTS.

     8.1  HOLDER'S RIGHT TO RECEIVE NOTICE. Nothing herein shall be construed as
conferring upon the Holders the right to vote or consent as a stockholder for
the election of directors or any other matter, or as having any rights
whatsoever as a stockholder of the Company. If, however, at any time prior to
the expiration of the Purchase Options and their exercise, any of the events
described in Section 8.2 shall occur, then, in one or more of said events, the
Company shall give written notice of such event at least fifteen days prior to
the date fixed as a record date or the date of closing the transfer books for
the determination of the stockholders entitled to such dividend, distribution,
conversion or exchange of securities or subscription rights, or entitled to vote
on such proposed dissolution, liquidation, winding up or sale. Such notice shall
specify such record date or the date of the closing of the transfer books, as
the case may be. Notwithstanding the foregoing, the Company shall deliver to
each Holder a copy of each notice given to the other stockholders of the Company
at the same time and in the same manner that such notice is given to the
stockholders.

     8.2  EVENTS REQUIRING NOTICE. The Company shall be required to give the
notice described in this Section 8 upon one or more of the following events: (i)
if the Company shall take a record of the holders of its shares of Common Stock
for the purpose of entitling them to receive a dividend or distribution payable
otherwise than in cash, or a cash dividend or distribution payable otherwise
than out of retained earnings, as indicated by the accounting treatment of such
dividend or distribution on the books of the Company, or (ii) the Company shall
offer to all the holders of its Common Stock any additional shares of capital
stock of the Company or securities convertible into or exchangeable for shares
of capital stock of the Company, or any option, right or warrant to subscribe
therefor, or (iii) a dissolution, liquidation or winding up of the Company
(other than in connection with a consolidation or merger) or a sale of all or
substantially all of its property, assets and business shall be proposed.

     8.3  NOTICE OF CHANGE IN EXERCISE PRICE. The Company shall, promptly after
an event requiring a change in the Exercise Price pursuant to Section 6 hereof,
send notice to the Holders of such event and change ("PRICE

                                        4
<Page>

NOTICE"). The Price Notice shall describe the event causing the change and the
method of calculating same and shall be certified as being true and accurate by
the Company's President and Chief Executive Officer.

     8.4  TRANSMITTAL OF NOTICES. All notices, requests, consents and other
communications under this Purchase Option shall be in writing and shall be
deemed to have been duly made when hand delivered, or mailed by express mail or
private courier service: (i) if to the registered Holder of the Purchase Option,
to the address of such Holder as shown on the books of the Company, or (ii) if
to the Company, to the following address or to such other address as the Company
may designate by notice to the Holders:


          Harbor Acquisition Corporation
          One Boston Place - Suite 3630
          Boston, Massachusetts 02108
          Attn:   Chief Executive Officer


9.   MISCELLANEOUS.

     9.1  AMENDMENTS. The Company and FBW may from time to time supplement or
amend this Purchase Option without the approval of any of the Holders in order
to cure any ambiguity, to correct or supplement any provision contained herein
that may be defective or inconsistent with any other provisions herein, or to
make any other provisions in regard to matters or questions arising hereunder
that the Company and FBW may deem necessary or desirable and that the Company
and FBW deem shall not adversely affect the interest of the Holders. All other
modifications or amendments shall require the written consent of and be signed
by the party against whom enforcement of the modification or amendment is
sought.

     9.2  HEADINGS. The headings contained herein are for the sole purpose of
convenience of reference, and shall not in any way limit or affect the meaning
or interpretation of any of the terms or provisions of this Purchase Option.

     9.3  ENTIRE AGREEMENT. This Purchase Option (together with the other
agreements and documents being delivered pursuant to or in connection with this
Purchase Option) constitutes the entire agreement of the parties hereto with
respect to the subject matter hereof, and supersedes all prior agreements and
understandings of the parties, oral and written, with respect to the subject
matter hereof.

     9.4  BINDING EFFECT. This Purchase Option shall inure solely to the
benefit of and shall be binding upon, the Holder and the Company and their
permitted assignees, respective successors, legal representative and assigns,
and no other person shall have or be construed to have any legal or equitable
right, remedy or claim under or in respect of or by virtue of this Purchase
Option or any provisions herein contained.

     9.5  GOVERNING LAW; SUBMISSION TO JURISDICTION. This Purchase Option shall
be governed by and construed and enforced in accordance with the laws of the
State of Maryland, without giving effect to conflict of laws. The Company hereby
agrees that any action, proceeding or claim against it arising out of, or
relating in any way to this Purchase Option shall be brought and enforced in the
courts of the State of Maryland or of the United States of America for the
District of Maryland, and irrevocably submits to such jurisdiction, which
jurisdiction shall be exclusive. The Company hereby waives any objection to such
exclusive jurisdiction and that such courts represent an inconvenient forum. Any
process or summons to be served upon the Company may be served by transmitting a
copy thereof by registered or certified mail, return receipt requested, postage
prepaid, addressed to it at the address set forth in Section 8 hereof. Such
mailing shall be deemed personal service and shall be legal and binding upon the
Company in any action, proceeding or claim. The Company and the Holder agree
that the prevailing party(ies) in any such action shall be entitled to recover
from the other party(ies) all of its reasonable attorneys' fees and expenses
relating to such action or proceeding and/or incurred in connection with the
preparation therefor.

     9.6  WAIVER, ETC. The failure of the Company or the Holder to at any time
enforce any of the provisions of this Purchase Option shall not be deemed or
construed to be a waiver of any such provision, nor to in any way affect

                                        5
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the validity of this Purchase Option or any provision hereof or the right of the
Company or any Holder to thereafter enforce each and every provision of this
Purchase Option. No waiver of any breach, non-compliance or non-fulfillment of
any of the provisions of this Purchase Option shall be effective unless set
forth in a written instrument executed by the party or parties against whom or
which enforcement of such waiver is sought; and no waiver of any such breach,
non-compliance or non- fulfillment shall be construed or deemed to be a waiver
of any other or subsequent breach or non-compliance.

     9.7  EXECUTION IN COUNTERPARTS. This Purchase Option may be executed in
one or more counterparts, and by the different parties hereto in separate
counterparts, each of which shall be deemed to be an original, but all of which
taken together shall constitute one and the same agreement, and shall become
effective when one or more counterparts has been signed by each of the parties
hereto and delivered to each of the other parties hereto.

     9.8  EXCHANGE AGREEMENT. As a condition of the Holder's receipt and
acceptance of this Purchase Option, Holder agrees that, at any time prior to the
complete exercise of this Purchase Option by Holder, if the Company and FBW
enter into an agreement ("EXCHANGE AGREEMENT") pursuant to which they agree that
all outstanding Purchase Options will be exchanged for securities or cash or a
combination of both, then Holder shall agree to such exchange and become a party
to the Exchange Agreement.

   [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK; SIGNATURE PAGE FOLLOWS.]

                                        6
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IN WITNESS WHEREOF, the Company has caused this Purchase Option to be signed by
its duly authorized officer as of the           day of ________, 2006.


                                       HARBOR ACQUISITION CORPORATION


                                       By:
                                          ------------------------------
                                             Robert J. Hanks,
                                             Chief Executive Officer

                                        7
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                                    EXHIBIT A

                  Form to be used to exercise Purchase Option:

Harbor Acquisition Corporation
One Boston Place - Suite 3630
Boston, Massachusetts 02108


Date: _________, 200__

     The undersigned hereby elects irrevocably to exercise all or a portion of
the within Purchase Option and to purchase          Units of Harbor Acquisition
Corporation and hereby makes payment of $            (at the rate of $       per
Unit) in payment of the Exercise Price pursuant thereto. Please issue the Common
Stock and Warrants as to which this Purchase Option is exercised in accordance
with the instructions given below.

                                       or

The undersigned hereby elects irrevocably to convert its right to purchase Units
purchasable under the within Purchase Option by surrender of the unexercised
portion of the attached Purchase Option (with a "Value" based of $    based on a
"Market Price" of $      ). Please issue the securities comprising the Units as
to which this Purchase Option is exercised in accordance with the instructions
given below.

                                               ---------------------------------
                                               NOTICE: The signature to this
                                               assignment must correspond with
                                               the name as written upon the face
                                               of the purchase option in every
                                               particular, without alteration or
                                               enlargement or any change
                                               whatever.

Signature(s) 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 SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO
S.E.C. RULE 17Ad-15).

                   INSTRUCTIONS FOR REGISTRATION OF SECURITIES

Name
      ----------------------------------------------------------
                             (Print in Block Letters)

Address
      ----------------------------------------------------------

                                       A-1
<Page>

                                    EXHIBIT B

                   Form to be used to assign Purchase Option:

                                   ASSIGNMENT

   (To be executed by the registered Holder to effect a transfer of the within
                                Purchase Option):

     FOR VALUE RECEIVED,                  does hereby sell, assign and transfer
unto the right to purchase          Units of Harbor Acquisition Corporation
("COMPANY") evidenced by the within Purchase Option and does hereby authorize
the Company to transfer such right on the books of the Company.

Dated:           , 200


                                            -----------------------------
                                            Signature

                                            -----------------------------
                                            NOTICE: The signature to this
                                            assignment must correspond with the
                                            name as written upon the face of the
                                            purchase option in every particular,
                                            without alteration or enlargement or
                                            any change whatever.


Signature(s) 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 SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO
S.E.C. RULE 17Ad-15).

                                       B-2