[Letterhead of Barclays Capital]

                                                         Barclays Capital
                                                         5 The North Colonnade
                                                         Canary Wharf
                                                         London E14 4BB

                                                         Tel +44 (0)20 7623 2323

To:         Wells Fargo Bank, N.A. as master servicer on behalf of the Wells
            Fargo Alternative Loan 2007-PA1 Trust (such trust, the "Issuing
            Entity") created under the Pooling and Servicing Agreement (as
            defined below)
Attn:       Wells Fargo Bank, N.A.
            9062 Old Annapolis Road
            Columbia, Maryland 21045
            Client Manager - Wells Fargo Alternative Loan Trust, Series 2007-PA1
            Telephone: 410-884-2000
            Facsimile:  410-715-2380
From:       BARCLAYS BANK PLC (LONDON HEAD OFFICE)
Attn:       5 The North Colonnade
            Canary Wharf
            E14 4BB
            Facsimile: 44(20) 77736461
            Phone: 44(20) 77736810
Date:       February 27, 2007
Reference:  1589950B / 1589949B

Dear Sir/Madam,

The purpose of this letter agreement is to confirm the terms and conditions of
the transaction entered into between Wells Fargo Bank, N.A. as master servicer
(the "Master Servicer") under the Pooling and Servicing Agreement (as defined
below) on behalf of the Issuing Entity and Barclays Bank PLC (each a "party" and
together "the parties") on the Trade Date specified below (the "Transaction").
This letter agreement constitutes a "Confirmation" as referred to in the ISDA
Master Agreement specified in paragraph 1 below. In this Confirmation, "Party A"
means Barclays Bank PLC and "Party B" means Wells Fargo Bank, N.A. as Master
Servicer on behalf of the Issuing Entity.

The definitions and provisions contained in the 2000 ISDA Definitions, as
published by the International Swaps and Derivatives Association, Inc. (the
"Definitions"), are incorporated into this Confirmation. In the event of any
inconsistency between the Definitions and this Confirmation, this Confirmation
will govern.

Other capitalized terms used herein (but not otherwise defined) shall have the
meaning specified in that certain Pooling and Servicing Agreement (the "Pooling
and Servicing Agreement"), to be dated as of February 27, 2007, among Wells
Fargo Asset Securities Corporation, as depositor (the "Depositor"), Wells Fargo
Bank, N.A., as Master Servicer and HSBC Bank USA, National Association, as
trustee.

1     This Confirmation evidences a complete binding agreement between the
      parties as to the terms of the Transaction to which this Confirmation
      relates. In addition, the parties agree that for the purposes of this
      Transaction, this Confirmation will supplement, form a part of, and be
      subject to an agreement in the form of the 1992 ISDA Master Agreement
      (Multicurrency-Cross Border) as if the parties had executed an agreement
      in such form (but without any Schedule except for the elections noted
      below) on the Trade Date of the Transaction (such agreement, the "Form
      Master Agreement"). In the event of any inconsistency between the
      provisions of the Form Master Agreement and this Confirmation, this
      Confirmation will prevail for the purpose of this Transaction.

      Each party represents to the other party and will be deemed to represent
      to the other party on the date on which it enters into this Transaction
      that (absent a written agreement between the parties that expressly
      imposes affirmative obligations to the contrary for that Transaction):

      (a)   Non-Reliance

            Party A has made its own independent decisions to enter into this
            Transaction and as to whether this Transaction is appropriate or
            proper for it based upon its own judgment and upon advice from such
            advisors as it has deemed necessary. Party B is acting, not
            individually or personally, but as Master Servicer and has been
            directed to enter into this Agreement by, and on behalf of, the
            Issuing Entity, which has made its own independent decisions to
            enter into this Transaction and as to whether this Transaction is
            appropriate or proper for it based upon its own judgment and upon
            advice from such advisors as it has deemed necessary. Each party is
            not relying on any communication (written or oral) of the other
            party as investment advice or as a recommendation to enter into this
            Transaction; it being understood that information and explanations
            related to the terms and conditions of this Transaction shall not be
            considered investment advice or a recommendation to enter into this
            Transaction. Further, such party has not received from the other
            party any assurance or guarantee as to the expected results of this
            Transaction.

      (b)   Evaluation and Understanding

            It is capable of evaluating and understanding (on its own behalf or
            through independent professional advice), and understands and
            accepts, the terms, conditions and risks of this Transaction. It is
            also capable of assuming, and assumes, the financial and other risks
            of this Transaction.

      (c)   Status of Parties

            The other party is not acting as an agent, fiduciary or advisor for
            it in respect of this Transaction.

2     The terms of the particular Transaction to which this Confirmation relates
      are as follows:

 Notional Amount:                         With respect to any Calculation Period
                                          the amount set forth on Schedule A
                                          attached hereto.

 Trade Date:                              February 8, 2007

 Effective Date:                          February 27, 2007

 Termination Date:                        May 25, 2011

 Fixed Amounts:

 Fixed Rate Payer:                        Party B

 Fixed Rate Payer Payment Date:           February 27, 2007

 Fixed Amount:                            USD[        ]

 Floating Amounts:

 Floating Rate Payer:                     Party A

 Cap Rate:                                5.51%

 Floating Rate Payer Period               The 25th day of each month of each
 End Dates:                               year, commencing on March 25, 2007,
                                          through and including the Termination
                                          Date, subject to no adjustment.

 Floating Rate Payer Payment Dates:       Early Payment shall be applicable. The
                                          Floating Rate Payer Payment Date shall
                                          be two Business Days prior to each
                                          Floating Rate Payer Period End Date.

 Floating Rate for Initial Calculation    To be determined.
 Period:

 Floating Rate Option:                    USD-LIBOR-BBA; provided, however, if
                                          the Floating Rate Option for any
                                          Calculation Period is greater than
                                          9.01% then the Floating Rate Option
                                          for such Calculation Period shall be
                                          deemed to be 9.01%.

 Floating Amount:                         To be determined in accordance with
                                          the following formula: the greater of
                                          (i) (Floating Rate Option - Cap Rate)
                                          * Notional Amount * Floating Rate Day
                                          Count Fraction and (ii) zero.

 Designated Maturity:                     1 Month

 Initial Floating Rate:                   5.32%

 Spread:                                  None

 Floating Rate Day Count Fraction:        30/360

 Reset Dates:                             The first day of each Calculation
                                          Period.

 Business Days for Payments:              New York

 Calculation Agent:                       Party A; provided, however, that if an
                                          Event of Default occurs with respect
                                          to Party A, then Party B shall be
                                          entitled to appoint a financial
                                          institution which would qualify as a
                                          Reference Market-Maker to act as
                                          Calculation Agent (such financial
                                          institution subject to Party A's
                                          consent).

3     Form Master Agreement

      (a)   "Specified Entity" means, in relation to Party A, for the purpose of
            Section 5(a)(v), Section 5(a)(vi), Section 5(a)(vii) and Section
            5(b)(iv): Not Applicable.

      (b)   "Specified Entity" means, in relation to Party B, for the purpose of
            Section 5(a)(v), Section 5(a)(vi), Section 5(a)(vii) and Section
            5(b)(iv): Not Applicable.

      (c)   "Specified Transaction" is not applicable to Party A or Party B for
            any purpose, and accordingly, Section 5(a)(v) shall not apply to
            Party A or Party B.

      (d)   The "Breach of Agreement" provisions of Section 5(a)(ii) of the
            Agreement will be inapplicable to Party A and Party B.

      (e)   The "Misrepresentation" provisions of Section 5(a)(v) of the
            Agreement will be inapplicable to Party A and Party B.

      (f)   The "Cross Default" provisions of Section 5(a)(vi) will not apply to
            Party A or Party B.

      (g)   The "Credit Event Upon Merger" provisions of Section 5(b)(iv) of the
            Form Master Agreement will not apply to Party A or to Party B.

      (h)   The "Automatic Early Termination" provision of Section 6(a) of the
            Form Master Agreement will not apply to Party A or to Party B.

      (i)   The Form Master Agreement will be governed by, and construed in
            accordance with, the laws of the State of New York without reference
            to its conflict of laws provisions (except for Sections 5-1401 and
            5-1402 of the New York General Obligations Law).

      (j)   The phrase "Termination Currency" means United States Dollars.

      (k)   For the purpose of Section 6(e) of the Form Master Agreement, Market
            Quotation and Second Method will apply.

4     Recording of Conversations

      Each party to this Transaction acknowledges and agrees to the tape (and/or
      other electronic) recording of conversations between the parties to this
      Transaction whether by one or other or both of the parties or their
      agents.

5     Credit Support Document

      In relation to Party A:             Credit Support Annex dated the date
                                          hereof and duly executed and delivered
                                          by Party A and Party B.

      In relation to Party B:             Not Applicable.

6     Credit Support Provider

      In relation to Party A:             Not Applicable, unless Party A has a
                                          person guarantee its payment
                                          obligations under this Agreement in
                                          order to remedy a Ratings Event, in
                                          which event such person shall be a
                                          Credit Support Provider.

      In relation to Party B:             Not Applicable.

7     Account Details

         Account for payments to Party A:

                 Correspondent: BARCLAYS BANK PLC NEW YORK
                 FEED: 026002574
                 Beneficiary:  BARCLAYS SWAPS
                 Beneficiary Account: 050-01922-8

         Account for payments to Party B:

                  Bank: Wells Fargo Bank, N.A.
                  ABA#: 121000248
                  Account Name: SAS Clearing
                  Acct #: 3970771416
                  FFC to: 50985402 - Reference WFALT 2007-PA1
                          Class A-9 Reserve Fund

8     Offices

      The Office of Party A for this Transaction is:

            London

      The Office of Party B for this Transaction is:

            Columbia, MD

9     Additional Provisions

            Fully-Paid Transactions

                 Notwithstanding the terms of Sections 5 and 6 of the Form
                 Master Agreement, if at any time and so long as Party B shall
                 have satisfied in full all its payment and delivery obligations
                 under Section 2(a)(i) of the Form Master Agreement and shall at
                 the time have no future payment or delivery obligations,
                 whether absolute or contingent, under such Section, then unless
                 Party A is required pursuant to appropriate proceedings to
                 return to Party B or otherwise returns to Party B (upon demand
                 of Party B, or otherwise) any portion of any such payment or
                 delivery: (i) the occurrence of an event described in Section
                 5(a) of the Form Master Agreement with respect to Party B shall
                 not constitute an Event of Default or a Potential Event of
                 Default with respect to Party B as the Defaulting Party; and
                 (ii) Party A shall be entitled to designate an Early
                 Termination Date pursuant to Section 6 of the Form Master
                 Agreement only as a result of the occurrence of a Termination
                 Event set forth in (i) either Section 5(b)(i) or 5(b)(ii) of
                 the Form Master Agreement with respect to Party A as the
                 Affected Party or (ii) Section 5(b)(iii) of the Form Master
                 Agreement with respect to Party A as the Burdened Party.

10    Compliance with Regulation AB

      (a)   Party A acknowledges that for so long as there are reporting
            obligations with respect to this Transaction under Regulation AB,
            the Depositor, acting on behalf of the Issuing Entity, is required
            under Regulation AB under the Securities Act of 1933, as amended,
            and the Securities Exchange Act of 1934, as amended ("Regulation
            AB"), to disclose certain information set forth in Regulation AB
            regarding Party A or its group of affiliated entities, if
            applicable, depending on the aggregate "significance percentage" of
            this Agreement and any other derivative contracts between Party A or
            its group of affiliated entities, if applicable, and Party B, as
            calculated from time to time in accordance with Item 1115 of
            Regulation AB.

      (b)   If the Depositor determines, reasonably and in good faith, that the
            significance percentage of this Agreement has increased to eight (8)
            percent or more but less than eighteen (18) percent, then the
            Depositor may request on the date of such determination (or, if such
            date of determination is not a Business Day, the immediately
            following Business Day) from Party A the same information set forth
            in Item 1115(b)(1) of Regulation AB that would have been required if
            the significance percentage had in fact increased to ten (10)
            percent, along with any necessary auditors' consent (such request, a
            "10% Cap Disclosure Request" and such requested information, subject
            to the last sentence of this paragraph, is the "10% Cap Financial
            Disclosure"). Party B (or the Depositor on its behalf) shall provide
            Party A with the calculations and any other information reasonably
            requested by Party A with respect to the Depositor's determination
            that led to the 10% Cap Disclosure Request. The parties hereto
            further agree that the 10% Cap Financial Disclosure provided to meet
            the 10% Cap Disclosure Request may be, solely at Party A's option,
            either the information set forth in Item 1115(b)(1) or Item
            1115(b)(2) of Regulation AB.

      (c)   Upon the occurrence of a 10% Cap Disclosure Request, Party A, at its
            own expense, shall (i) provide the Depositor with the 10% Cap
            Financial Disclosure, (ii) subject to Rating Agency Confirmation,
            secure another entity to replace Party A as party to this Agreement
            on terms substantially similar to this Agreement which entity is
            able to (A) provide the 10% Cap Financial Disclosure and (B) provide
            an indemnity to the Depositor, reasonably satisfactory to the
            Depositor, in relation to the 10% Cap Financial Disclosure or (iii)
            subject to Rating Agency Confirmation, obtain a guaranty of Party
            A's obligations under this Agreement from an affiliate of Party A
            that is able to (A) provide the 10% Cap Financial Disclosure, such
            that disclosure provided in respect of the affiliate will, in the
            judgment of counsel to the Depositor, satisfy any disclosure
            requirements applicable to Party A, and cause such affiliate to
            provide 10% Cap Financial Disclosure and (B) provide an indemnity to
            the Depositor, reasonably satisfactory to the Depositor, in relation
            to the 10% Cap Financial Disclosure. Any such 10% Cap Financial
            Disclosure provided pursuant to this paragraph (c) shall be in a
            form suitable for conversion to the format required for filing by
            the Depositor with the Securities and Exchange Commission via the
            Electronic Data Gathering and Retrieval System (EDGAR). If permitted
            by Regulation AB, any required 10% Cap Financial Disclosure may be
            provided by incorporation by reference from reports filed pursuant
            to the Securities Exchange Act.

      (d)   If the Depositor determines, reasonably and in good faith, that the
            significance percentage of this Agreement has increased to eighteen
            (18) percent or more, then the Depositor may request on the date of
            such determination (or, if such date of determination is not a
            Business Day, the immediately following Business Day) from Party A
            the same information set forth in Item 1115(b)(2) of Regulation AB
            that would have been required if the significance percentage had in
            fact increased to twenty (20) percent, along with any necessary
            auditors consent (such request, a "20% Cap Disclosure Request" and
            such requested information is the "20% Cap Financial Disclosure").
            Party B (or the Depositor on its behalf) shall provide Party A with
            the calculations and any other information reasonably requested by
            Party A with respect to the Depositor's determination that led to
            the 20% Cap Disclosure Request.

      (e)   Upon the occurrence of a 20% Cap Disclosure Request, Party A, at its
            own expense, shall (i) provide the Depositor with the 20% Cap
            Financial Disclosure, (ii) subject to Rating Agency Confirmation,
            secure another entity to replace Party A as party to this Agreement
            on terms substantially similar to this Agreement which entity is
            able to (A) provide the 20% Cap Financial Disclosure and (B) provide
            an indemnity to the Depositor, reasonably satisfactory to the
            Depositor, in relation to the 20% Cap Financial Disclosure or (iii)
            subject to Rating Agency Confirmation, obtain a guaranty of Party
            A's obligations under this Agreement from an affiliate of Party A
            that is able to (A) provide the 20% Cap Financial Disclosure, such
            that disclosure provided in respect of the affiliate will, in the
            judgment of counsel to the Depositor, satisfy any disclosure
            requirements applicable to Party A, and cause such affiliate to
            provide 20% Cap Financial Disclosure and (B) provide an indemnity to
            the Depositor, reasonably satisfactory to the Depositor, in relation
            to the 20% Cap Financial Disclosure. Any such 20% Cap Financial
            Disclosure provided pursuant to this paragraph (e) shall be in a
            form suitable for conversion to the format required for filing by
            the Depositor with the Securities and Exchange Commission via the
            Electronic Data Gathering and Retrieval System (EDGAR). If permitted
            by Regulation AB, any required 20% Cap Financial Disclosure may be
            provided by incorporation by reference from reports filed pursuant
            to the Securities Exchange Act.

11    Additional Termination Events

      The following Additional Termination Events will apply:

      (a)   a Ratings Event has occurred and Party A has not, within thirty (30)
            days, complied with Section 12 below, then an Additional Termination
            Event shall have occurred with respect to Party A and Party A shall
            be the sole Affected Party with respect to such Additional
            Termination Event.

      (b)   If (A) the Depositor still has a reporting obligation with respect
            to this Transaction pursuant to Regulation AB and (B) Party A has
            not, within 30 days after receipt of a 10% Cap Disclosure Request
            complied with the provisions set forth in clauses (b) and (c) of
            Paragraph 10 above (provided that if the significance percentage is
            10% or more and less than 20% when the 10% Cap Disclosure Request is
            made or reaches 10% after a 10% Cap Disclosure Request has been made
            to Party A, Party A must comply with the provisions set forth in
            clauses (b) and (c) of Paragraph 10 above within 3 calendar days of
            Party A being informed of the significance percentage reaching 10%
            or more), then an Additional Termination Event shall have occurred
            with respect to Party A and Party A shall be the sole Affected Party
            with respect to such Additional Termination Event.

      (c)   If (A) the Depositor still has a reporting obligation with respect
            to this Transaction pursuant to Regulation AB and (B) Party A has
            not, within 30 days after receipt of a 20% Cap Disclosure Request
            complied with the provisions set forth in clauses (d) and (e) of
            Paragraph 10 above (provided that if the significance percentage is
            20% or more when the 20% Cap Disclosure Request is made or reaches
            20% after a 20% Cap Disclosure Request has been made to Party A,
            Party A must comply with the provisions set forth in clauses (d) and
            (e) of Paragraph 10 above within 3 calendar days of Party A being
            informed of the significance percentage reaching 20% or more), then
            an Additional Termination Event shall have occurred with respect to
            Party A and Party A shall be the sole Affected Party with respect to
            such Additional Termination Event.

12    Ratings Event

      If a Ratings Event (as defined below) occurs with respect to Party A (or
      any applicable Credit Support Provider), then Party A shall, at its own
      expense, (i) assign this Transaction within thirty (30) days of such
      Ratings Event to a third party that meets or exceeds, or as to which any
      applicable credit support provider meets or exceeds, the Approved Ratings
      Thresholds (as defined below) on terms substantially similar to this
      Confirmation, which party is approved by Party B, which approval shall not
      be unreasonably withheld, (ii) obtain a guaranty of, or a contingent
      agreement of, another person with the Approval Rating Thresholds to honor
      Party A's obligations under this Agreement, provided that such other
      person is approved by Party B, such approval not to be unreasonably
      withheld, (iii) post collateral the Credit Support Annex, or (iv)
      establish any other arrangement satisfactory to Fitch Ratings ("Fitch"),
      Standard & Poor's, a division of The McGraw Hill Companies ("S&P") and
      Moody's Investor Service, Inc. ("Moody's"), which will be sufficient to
      restore the immediately prior ratings of the Certificates. For purposes of
      this Transaction, a "Ratings Event" shall occur with respect to Party A
      (or any applicable credit support provider) if its short term unsecured
      and unsubordinated debt rating is withdrawn or reduced below "F1" by
      Fitch, its short term unsecured and unsubordinated debt rating is
      withdrawn or reduced below "A-1" by S&P, or its short-term unsecured
      unsubordinated debt rating is withdrawn or reduced below "P-1" by Moody's
      (including in connection with a merger, consolidation or other similar
      transaction by Party A or any applicable credit support provider) such
      ratings being referred to herein as the "Approved Rating Thresholds,"
      unless, within thirty (30) days hereafter, each of Fitch and Moody's has
      reconfirmed the ratings of the Certificates, as applicable, which was in
      effect immediately prior thereto (such confirmation a "Rating Agency
      Confirmation").

13    Waiver of Right to Trial by Jury

      EACH PARTY HEREBY IRREVOCABLY WAIVES ANY AND ALL RIGHTS TO TRIAL BY JURY
      WITH RESPECT TO ANY LEGAL PROCEEDING ARISING OUT OF OR RELATING TO THIS
      TRANSACTION.

14    Eligible Contract Participant

      Each party represents to the other party that it is an "eligible contract
      participant" as defined in Section 1a(12) of the U.S. Commodity Exchange
      Act, as amended.

15    Multibranch Party

      For purpose of Section 10(c) of the Form Master Agreement: (a) Party A is
      a Multibranch Party; and (b) Party B is not a Multibranch Party.

16    Other provisions

      (d)   Addresses for notices. As set forth on page 1 hereof.

      (e)   For the purpose of Section 13(c) of the Form Master Agreement: (i)
            Party A appoints as its Process Agent, not applicable; and (ii)
            Party B appoints as its Process Agent, not applicable.

      (f)   Section 12(a)(ii) of the Form Master Agreement is deleted in its
            entirety.

      (g)   Documents to be Delivered. For the purpose of Section 4(a) of the
            Form Master Agreement:

<TABLE>
<CAPTION>
Party required to
deliver document            Form/Document/Certificate                            Date by which to be         Covered by Section 3(d)
                                                                                      delivered                  Representation
------------------------------------------------------------------------------------------------------------------------------------
<S>                     <C>                                                     <C>                          <C>
Party A and Party B      A certificate of an authorized officer of the           Upon the execution                  Yes
                         party, as to the incumbency and authority of the        and delivery of
                         respective officers of the party signing this           this Confirmation
                         Confirmation

Party A                  Legal opinion satisfactory in form and substance        Upon execution and                  No
                         to Party B relating to the enforceability of            delivery of this
                         Party A's obligations under this Agreement              Confirmation

Party B                  The Pooling and Servicing Agreement                     Within 30 days of                   Yes
                                                                                 February 27, 2007
</TABLE>

(h)   Limitation of Liability

      It is expressly understood and agreed by the parties hereto that (a) this
      letter agreement is executed and delivered by Wells Fargo Bank, N.A., not
      individually or personally but solely as the Master Servicer on behalf of
      the Issuing Entity, in the exercise of the powers and authority conferred
      and vested in it under the Pooling and Servicing Agreement, (b) the
      representations, undertakings and agreements herein are made on the part
      of the Issuing Entity and intended not as personal representations,
      undertakings and agreements by Wells Fargo Bank, N.A. but are made and
      intended for the purpose of binding only the Issuing Entity, (c) nothing
      herein contained shall be construed as creating any liability on Wells
      Fargo Bank, N.A., individually or personally, to perform any covenant
      either expressed or implied contained herein, all such liability, if any,
      being expressly waived by the parties who are signatories to this letter
      agreement and by any person claiming by, through or under such parties,
      and (d) under no circumstances shall Wells Fargo Bank, N.A. in its
      individual capacity be personally liable for the payment of any
      indebtedness or expenses of the Issuing Entity or be personally liable for
      the breach or failure of any obligation, representation, warranty or
      covenant made or undertaken under this letter agreement.

(i)   This letter agreement may be executed in several counterparts, each of
      which shall be deemed an original but all of which together shall
      constitute one and the same instrument.

(j)   USA PATRIOT Act Notice. Party A hereby notifies Party B that pursuant to
      the requirements of the USA PATRIOT ACT (Title III of Pub. L. 107-56
      (signed into law October 26, 2001)), as amended (the "Act"), it is
      required to obtain, verify and record information that identifies Party B,
      which information includes the name and address of Party B and other
      information that will allow Party A to identify Party B in accordance with
      the Act.

(k)   Proceedings

      Party A shall not institute against or cause any other person to institute
      against, or join any other person in instituting against, Party B, any
      bankruptcy, reorganization, arrangement, insolvency or liquidation
      proceedings, or other proceedings under any federal or state bankruptcy,
      dissolution or similar law, for a period of one year and one day following
      indefeasible payment in full of the Certificates, provided that nothing
      herein shall preclude, or be deemed to estop Party A from taking any
      action in any case or proceeding voluntarily filed or commenced by or on
      behalf of Party B or in any involuntary case or proceeding after it has
      been commenced.

(l)   Set-off

      Notwithstanding any provision of this Agreement (other than 2(c) and 6(e))
      or any other existing or future agreement, each party irrevocably waives
      any and all rights it may have to set-off, net, recoup or otherwise
      withhold or suspend or condition payment or performance of any obligation
      between it and the other party hereunder against any obligation between it
      and the other party under any other agreements.

(m)   Section 1(c)

      For purposes of Section 1(c) of the Form Master Agreement, this
      Transaction shall be the sole Transaction under the Agreement.

(n)   Transfer and Amendment

      Subject to Part 13 herein, no transfer, amendment, waiver, supplement,
      assignment or other modification of this Transaction shall be permitted by
      either party unless the Rating Agency Condition has been satisfied.

                  [remainder of page intentionally left blank]

<PAGE>


The time of dealing will be confirmed by Barclays upon written request. Barclays
is regulated by the Financial Services Authority. Barclays is acting for its own
account in respect of this Transaction.

Please confirm that the foregoing correctly sets forth all the terms and
conditions of our agreement with respect to the Transaction by responding within
three (3) Business Days by promptly signing in the space provided below and both
(i) faxing the signed copy to Incoming Transaction Documentation, Barclays
Capital Global OTC Transaction Documentation & Management, Global Operations,
Fax +(44) 20-7773-6810/6857, Tel +(44) 20-7773-6901/6904/6965, and (ii) mailing
the signed copy to Barclays Bank PLC, 5 The North Colonnade, Canary Wharf,
London E14 4BB, Attention of Incoming Transaction Documentation, Barclays
Capital Global OTC Transaction Documentation & Management, Global Operation.
Your failure to respond within such period shall not affect the validity or
enforceability of the Transaction against you. This facsimile shall be the only
documentation in respect of the Transaction and accordingly no hard copy
versions of this Confirmation for this Transaction shall be provided unless the
Counterparty requests.

--------------------------------------------------------------------------------
For and on behalf of                  For and on behalf of
BARCLAYS BANK PLC                     Wells Fargo Bank, N.A., not individually
                                      but solely as master servicer under the
                                      Pooling and Servicing Agreement on behalf
                                      of Wells Fargo Alternative Loan 2007-PA1
                                      Trust
--------------------------------------------------------------------------------

 /s/ Shain Kalmanowitz                 /s/ Carla S. Walker
------------------------------------ -------------------------------------------
Name:   Shain Kalmanowitz              Name:   Carla S. Walker
Title:  Authorized Signatory           Title:  Vice President
Date:   February 27, 2007              Date:   February 27, 2007
--------------------------------------------------------------------------------

Barclays Bank PLC and its Affiliates, including Barclays Capital Inc., may share
with each other information, including non-public credit information, concerning
its clients and prospective clients. If you do not want such information to be
shared, you must write to the Director of Compliance, Barclays Bank PLC, 200
Park Avenue, New York, NY 10166.

<PAGE>

Schedule A to the Confirmation dated as of February 27, 2007
Reference: 1589950B / 1589949B

From and including          To but excluding         Notional Amount (USD):
    2/27/2007                   3/25/2007                       0
    3/25/2007                   4/24/2007                 30,000,000.00
    4/25/2007                   5/24/2007                 30,000,000.00
    5/25/2007                   6/24/2007                 30,000,000.00
    6/25/2007                   7/24/2007                 30,000,000.00
    7/25/2007                   8/24/2007                 30,000,000.00
    8/25/2007                   9/24/2007                 30,000,000.00
    9/25/2007                  10/24/2007                 30,000,000.00
    10/25/2007                 11/24/2007                 30,000,000.00
    11/25/2007                 12/24/2007                 30,000,000.00
    12/25/2007                  1/24/2008                 30,000,000.00
    1/25/2008                   2/24/2008                 30,000,000.00
    2/25/2008                   3/24/2008                 30,000,000.00
    3/25/2008                   4/24/2008                 30,000,000.00
    4/25/2008                   5/24/2008                 30,000,000.00
    5/25/2008                   6/24/2008                 30,000,000.00
    6/25/2008                   7/24/2008                 30,000,000.00
    7/25/2008                   8/24/2008                 30,000,000.00
    8/25/2008                   9/24/2008                 30,000,000.00
    9/25/2008                  10/24/2008                 30,000,000.00
    10/25/2008                 11/24/2008                 30,000,000.00
    11/25/2008                 12/24/2008                 30,000,000.00
    12/25/2008                  1/24/2009                 30,000,000.00
    1/25/2009                   2/24/2009                 30,000,000.00
    2/25/2009                   3/24/2009                 30,000,000.00
    3/25/2009                   4/24/2009                 8,738,189.91
    4/25/2009                   5/24/2009                 8,187,767.94
    5/25/2009                   6/24/2009                 7,671,946.30
    6/25/2009                   7/24/2009                 7,190,022.90
    7/25/2009                   8/24/2009                 6,737,629.93
    8/25/2009                   9/24/2009                 6,299,106.66
    9/25/2009                  10/24/2009                 5,874,180.92
    10/25/2009                 11/24/2009                 5,462,585.27
    11/25/2009                 12/24/2009                 5,064,057.00
    12/25/2009                  1/24/2010                 4,678,338.00
    1/25/2010                   2/24/2010                 4,305,174.70
    2/25/2010                   3/24/2010                 3,944,318.00
    3/25/2010                   4/24/2010                 3,595,523.19
    4/25/2010                   5/24/2010                 3,258,549.86
    5/25/2010                   6/24/2010                 2,933,161.87
    6/25/2010                   7/24/2010                 2,619,127.20
    7/25/2010                   8/24/2010                 2,316,217.98
    8/25/2010                   9/24/2010                 2,024,210.34
    9/25/2010                  10/24/2010                 1,742,884.37
    10/25/2010                 11/24/2010                 1,472,024.07
    11/25/2010                 12/24/2010                 1,211,417.25
    12/25/2010                  1/24/2011                  960,855.50
    1/25/2011                   2/24/2011                  720,134.09
    2/25/2011                   3/24/2011                  489,051.94
    3/25/2011                   4/24/2011                  267,411.55
    4/25/2011                   5/24/2011                   55,018.93
    5/25/2011                   6/24/2011                       0

<PAGE>

                                     ISDA(R)

              International Swaps and Derivatives Association, Inc.


                              CREDIT SUPPORT ANNEX

                                     to the

                    ISDA Master Agreement deemed entered into

                          dated as of February 27, 2007

                                     between

         BARCLAYS BANK PLC                  WELLS FARGO BANK, N.A., not
                                            individually but solely as master
                                            servicer under the Pooling and
                                            Servicing Agreement on behalf of
                                            Wells Fargo Alternative Loan
                                            2007-PA1 Trust

                                       and
....................................         ..................................
            ("Party A")                                ("Party B")

This Annex supplements, forms part of, and is subject to, the above-referenced
Agreement, is part of its Schedule and is a Credit Support Document under this
Agreement with respect to each party.

Paragraph 13.

(a)   Security Interest for "Obligations". The term "Obligations" as used in
      this Annex includes the following additional obligations:

            With respect to Party A: None.

            With respect to Party B: None.

(b)   Credit Support Obligations.

      (i)   Delivery Amount, Return Amount and Credit Support Amount.

            (A)   "Delivery Amount" has the meaning specified in Paragraph 3(a)
                  , except that the words "upon a demand made by the Secured
                  Party on or promptly following a Valuation Date" shall be
                  deleted and replaced with the words "not later than the close
                  of business on the next Local Business Day following a
                  Valuation Date"; and

            (B)   "Return Amount" has the meaning specified in Paragraph 3(b).

            (C)   "Credit Support Amount". shall not have the meaning specified
                  in Paragraph 3(b) and, instead, will have the following
                  meaning:

                  "Credit Support Amount" means, (a) for any Valuation Date on
                  which a Ratings Event (as defined in the Agreement) has
                  occurred and is continuing and Party A has not otherwise
                  complied with Section 12 of this Agreement, the Secured
                  Party's Modified Exposure for that Valuation Date.

      (ii)  Eligible Credit Support. On any date, the following items will
            qualify as "Eligible Credit Support" for each party:

<TABLE>
<CAPTION>
                                                                                       Valuation
                                                                                       Percentage
                                                                                       ----------
<S>                                                                                    <C>
            (A)   cash in U.S Dollars                                                     100%

            (B)   negotiable debt obligations issued after 18 July 1984 by                98.0%
                  the U.S. Treasury Department having a residual maturity
                  on such date of less than 1 year (with local and foreign
                  currency issuer ratings of Moody's Aa2 and S&P AA or
                  above)

            (C)   negotiable debt obligations issued after 18 July 1984 by                To be agreed between
                  the U.S. Treasury Department having a residual maturity                 Party A and Party B
                  on such date equal to or greater than 1 year but less                   with the approval of
                  than 5 years (with local and foreign currency issuer                    the Rating Agencies
                  ratings of Moody's Aa2 and S&P AA or above)

            (D)   negotiable debt obligations issued after l8 July 1984 by                To be agreed between
                  the U.S. Treasury Department having a residual maturity                 Party A and Party B
                  on such date equal to or greater than 5 years but less                  with the approval of
                  than 10 years (with local and foreign currency issuer                   the Rating Agencies
                  ratings of Moody's Aa2 and S&P AA or above)

            (E)   negotiable debt obligations of the Government National                  To be agreed between
                  Mortgage Association, the Federal National Mortgage                     Party A and Party B
                  Association, the Federal Home Loan Mortgage Corporation,                with the approval of
                  the Student Loan Marketing Association or a Federal Home                the Rating Agencies
                  Loan Bank (all entities rated Moody's Aal and S&P AA+ or
                  above) with a residual maturity on such date equal to or
                  greater than 1 year but less than 3 years.

            (F)   negotiable debt obligations of the Government National                  To be agreed between
                  Mortgage Association, the Federal National Mortgage                     Party A and Party B
                  Association, the Federal Home Loan Mortgage Corporation,                with the approval of
                  the Student Loan Marketing Association or a Federal Home                the Rating Agencies
                  Loan Bank (all entries rated Moody's Aa 1 and S&P AA+ or
                  above) with a residual maturity on such date equal to or
                  greater than 3 years but less than 5 years.

            (G)   negotiable debt obligations of the Government National                  To be agreed between
                  Mortgage Association, the Federal National Mortgage                     Party A and Party B
                  Association, the Federal Home Loan Mortgage Corporation,                with the approval of
                  the Student Loan Marketing Association or a Federal Home                the Rating Agencies
                  Loan Bank (all entries rated Moody's Aal and S&P AA+ or
                  above) with a residual maturity on such date equal to or
                  greater than 5 years but less than 7 years.

            (H)   negotiable debt obligations of the Government National                  To be agreed between
                  Mortgage Association, the Federal National Mortgage                     Party A and Party B
                  Association, the Federal Home Loan Mortgage Corporation,                with the approval of
                  the Student Loan Marketing Association or a Federal Home                the Rating Agencies
                  Loan Bank (all entries rated Moody's Aal and S&P AA+ or
                  above) with a residual maturity on such date equal to or
                  greater than 7 years but less than 10 years.
</TABLE>

      For the avoidance of doubt, where negotiable debt obligations are rated by
      only one of the above relevant rating agencies, the rating applied will be
      based on the rating of that agency. Notwithstanding the foregoing, the
      Eligible Collateral referenced above may only be posted if S&P has
      assigned a rating to such Eligible Collateral.

      Where the ratings of the relevant agencies differ with respect to the same
      negotiable debt obligation, the lower of the ratings shall apply.

      In addition, upon a Ratings Event, Party A shall agree the Valuation
      Percentage in relation to (C) through (H) above with the relevant rating
      agency, which shall be S&P, Moody's and Fitch (to the extent such ratings
      agency has provided a rating for the underlying Certificates); provided,
      however, that if Party A is required to post collateral in accordance with
      the terms of this Agreement it shall post only (A) and (B) above until
      such time as the Valuation Percentages are agreed.

      (iii) Other Eligible Support. Such Other Eligible Support as the Pledgor
            may designate; provided, at the expense of the Pledgor, the prior
            written consent of the relevant rating agency, which shall be S&P,
            Moody's and Fitch (to the extent such ratings agency has provided a
            rating for the underlying Certificates)), shall have been obtained.
            For the avoidance of doubt there are no items which qualify as Other
            Eligible Support as of the date of this Annex.

      (iv)  Thresholds.

            (A)   "Independent Amount" means zero.

            (B)   "Threshold" means for Party A:

                  1.    infinity, unless (i) a Ratings Event occurs and is
                        continuing and (ii) Party A has not otherwise complied
                        with Section 12 of this Agreement, then its Threshold
                        shall be zero, or

                  2.    in the event that Party A has otherwise complied with
                        Section 12 of this Agreement, its Threshold shall
                        continue to be infinity.

                        "Threshold" means, for Party B: infinity

            (C)   "Minimum Transfer Amount" means USD 100,000, provided,
                  however, with respect to the Secured Party at any time when
                  the Secured Party is a Defaulting Party, "Minimum Transfer
                  Amount" means zero.

            (D)   Rounding: The Delivery Amount and the Return Amount will not
                  be rounded.

(c)   Valuation and Timing.

      (i)   "Valuation Agent" means Party A. The valuation agent's calculations
            shall be made in accordance with market practices using commonly
            accepted third party sources such as Bloomberg or Reuters.

      (ii)  "Valuation Date" means each Local Business Day which, if treated as
            a Valuation Date, would result in a Delivery Amount or Return
            Amount.

      (iii) "Valuation Time" means the close of business in the city of the
            Valuation Agent on the Local Business Day before the Valuation Date
            or date of calculation, as applicable, provided that the
            calculations of Value and Exposure will be made as of approximately
            the same time on the same date.

      (iv)  "Notification Time" means 11:00 a.m., New York time, on a Local
            Business Day.

(d)   Conditions Precedent and Secured Party's Rights and Remedies. The
      following Termination Event will be a "Specified Condition" for the party
      specified (that party being the Affected Party if the Termination Event
      occurs with respect to that party): None.

(e)   Substitution.

      (i)   "Substitution Date" has the meaning specified in Paragraph 4(d)(ii).

      (ii)  Consent. The Pledgor is not required to obtain the Secured Party's
            consent for any substitution purusant to Paragraph 4(d).

(f)   Dispute Resolution.

      (i)   "Resolution Time" means 1:00 p.m. New York time on the Local
            Business Day following the date on which the notice of the dispute
            is given under Paragraph 5.

            Value. For the purpose of Paragraphs 5(i)(C) and 5(ii), on any date,
            the Value of Eligible Credit Support will be calculated as follows:

            For Eligible Credit Support comprised of cash, the amount of such
            cash.

            For Eligible Collateral comprising securities; the sum of (a)(x) the
            last bid price on such date for such securities on the principal
            national securities exchange on which such securities are listed,
            multiplied by the applicable Valuation Percentage or (y) where any
            such securities are not listed on a national securities exchange,
            the bid price for such securities quoted as at the close of business
            on such date by any principal market maker for such securities
            chosen by the Valuation Agent, multiplied by the applicable
            Valuation Percentage or (z) if no such bid price is listed or quoted
            for such date, the last bid price listed or quoted (as the case may
            be), as of the day next preceding such date on which such prices
            were available; multiplied by the applicable Valuation Percentage;
            plus (b) the accrued interest on such securities (except to the
            extent that such interest shall have been paid to the Pledgor
            pursuant to Paragraph 6(d)(ii) or included in the applicable price
            referred to in subparagraph (a) above) as of such date.

      (ii)  Alternative. The provisions of Paragraph 5 will apply; provided that
            the obligation of the appropriate party to deliver the undisputed
            amount to the other party will not arise prior to the time that
            would otherwise have applied to the Transfer pursuant to, or deemed
            made, under Paragraph 3 if no dispute had arisen.

(g)   Holding and Using Posted Collateral.

      (i)   Eligibility to Hold Posted Collateral; Custodians.

            Party B is not and will not be entitled to hold Posted Collateral.
            Party B's Custodian will be entitled to hold Posted Collateral
            pursuant to Paragraph 6(b); provided that the Custodian for Party B
            shall be the same banking institution that acts as Master Servicer
            for the Certificates (as defined in the Pooling and Servicing
            Agreement) for Party B.

            Initially, the Custodian for Party B is: Wells Fargo Bank, N.A.

      (ii)  Use of Posted Collateral. The provisions of Paragraph 6(c) will not
            apply to Party B; therefore, Party B will not have any of the rights
            specified in Paragraph 6(c)(i) or 6 (c)(ii); provided, however, that
            Party B or its Custodian shall have the right to register any Posted
            Collateral that constitutes a book-entry security in the name of its
            Custodian; and provided, further, that the Trustee shall invest Cash
            Posted Credit Support in such investments as designated by Party A,
            with losses (net of gains) incurred in respect of such investments
            to be for the account of Party A.

(h)   Distributions and Interest Amount.

      (i)   Interest Rate. The "Interest Rate" will be the rate earned on Cash
            Posted Credit Support pursuant to clause (g)(ii) above.

      (ii)  Transfer of Interest Amount. The Transfer of the Interest Amount
            will be made on each Distribution Date.

      (iii) Alternative to Interest Amount. The provisions of Paragraph 6(d)(ii)
            will not apply.

(i)   Additional Representation(s).

      There are no additional representations by either party.

(j)   Other Eligible Support and Other Posted Support.

      (i)   "Value" with respect to Other Eligible Support and Other Posted
            Support shall have such meaning as the parties shall agree in
            writing from time to time.

      (ii)  "Transfer" with respect to Other Eligible Support and Other Posted
            Support shall have such meaning as the parties shall agree in
            writing from time to time.

(k)   Demands and Notices.

      All demands, specifications and notices under this Annex will be made
      pursuant to the Notices Section of this Agreement, save that any demand,
      specification or notice:

      (i)   shall be given to or made at the following addresses:

      If to Party A:

                 5 The North Colonnade
                 Canary Wharf
                 London E14 4BB, England
                 Attention:  Swaps Documentation
                 Facsimile No.:  0207-773-6857/6858
                 Telephone No.:  0207-773-6915/6904

      with a copy to:

                 General Counsel's Office
                 200 Park Avenue
                 New York, N.Y. 10166

      Notices to Party A shall not be deemed effective unless delivered to the
      London address set forth above.

      If to Party B:

            Wells Fargo Bank, N.A.
            9062 Old Annapolis Road
            Columbia, Maryland 21045
            Attn: Client Manager - WFALT 2007-PA1
            Facsimile: 410-715-2380
            Telephone: 410-884-2000

      or at such other address as the relevant party may from time to time
      designate by giving notice (in accordance with the terms of this
      paragraph) to the other party;

      (ii)  shall (unless otherwise stated in this Annex) be deemed to be
            effective at the time such notice is actually received unless such
            notice is received on a day which is not a Local Business Day or
            after the Notification Time on any Local Business Day in which event
            such notice shall be deemed to be effective on the next succeeding
            Local Business Day.

(l)   Address for Transfers.

      Party B: To be notified by Party B to Party A at the time of the request
      for Transfer.


(m)   Other Provisions.

      (i)   Additional Definitions. As used in this Annex:

            "Local Business Day" means: (i) any day on which commercial banks
            are open for business (including dealings in foreign exchange and
            foreign currency deposits) in London, New York and the location of
            the Trustee, and (ii) in relation to a Transfer of Eligible Credit
            Support, a day on which the clearance system agreed between the
            parties for the delivery of Eligible Credit Support is open for
            acceptance and execution of settlement instructions (or in the case
            of a Transfer of Cash or other Eligible Credit Support for which
            delivery is contemplated by other means, a day on which commercial
            banks are open for business (including dealings for foreign exchange
            and foreign deposits) in New York and such other places as the
            parties shall agree).

      (ii)  Holding Collateral. The Secured Party shall cause any Custodian
            appointed hereunder to open and maintain a segregated account and to
            hold, record and identify all the Posted Collateral in such
            segregated account and, subject to Paragraph 8(a), such Posted
            Collateral shall at all times be and remain the property of the
            Pledgor and shall at no time constitute the property of, or be
            commingled with the property of, the Secured Party or the Custodian.

      (iii) Agreement as to Single Secured Party and Pledgor. Party A and Party
            B agree that, notwithstanding anything to the contrary in this
            Annex, (a) the term "Secured Party" as used in this Annex means only
            Party B, (b) the term "Pledgor" as used in this Annex means only
            Party A, (c) only Party A makes the pledge and grant in Paragraph 2,
            the acknowledgement in the final sentence of Paragraph 8(a) and the
            representations in Paragraph 9 and (d) Party A shall have no
            obligations under this Annex other than during a Collateral
            Requirement Period.

      (iv)  Form of Annex. The parties hereby agree that the text of the body of
            this Annex is intended to be the printed form of ISDA Credit Support
            Annex (Bilateral Form - ISDA Agreements Subject to New York Law
            version) as published and copyrighted by the International Swaps and
            Derivatives Association, Inc.

      (v)   Exposure. The Parties agree that in the event of a Ratings Event
            relating to an action taken by S&P, the Valuation Agent shall
            internally verify its calculation of the Secured Party's Exposure by
            reporting its calculation thereof to S&P on a weekly basis. In
            addition, in the case where the long term unubordinated and
            unsecured debt of Party A ceases to be rated at least BBB+ by S&P,
            the Valuation Agent shall externally verify its calculation of the
            Secured Party's Exposure by seeking two quotations from Reference
            Market-makers at the end of each month (such quotations being for
            amounts payable as described in the definition of "Market
            Quotations" in the Agreement where the date on which such quotations
            are sought is the Early Termination Date and the Transaction entered
            into pursuant to the Agreement is the only Termination Transaction).
            In the case where external verification of the Exposure calculation
            is required, the Valuation Agent must (i) obtain at least two such
            quotations (ii) may not obtain the quotations referred to above from
            the same Reference Market-maker in excess of four times during any
            12 month period. Furthermore, the Exposure valuations should reflect
            the higher of two bids from Reference Market-makers that would be
            eligible and willing to provide the market quotation in the absence
            of the current provider and (iii) must submit to S&P the two bids
            provided by external parties. The collateral requirement should be
            based on the greater of the internal and external verifications. In
            the event the verification procedures set forth above indicate that
            there is a deficiency in the amount of Eligible Collateral that has
            been posted to the Secured Party, the Pledgor shall post the amount
            of Eligible Collateral necessary to cure such deficiency to the
            Secured Party within three Local Business Days.

      (vi)  Expenses. Notwithstanding Paragraph 10, the Pledgor will be
            responsible for, and will reimburse the Secured Party for, all
            transfer and other taxes and other costs involved in the transfer of
            Eligible Collateral.

      (vii) Additional Definitions. As used in this Annex:

            "Ratings Event" means a "Ratings Event" (as defined in the
            Agreement).

            "Modified Exposure" means, for any Valuation Date, an amount equal
            to the greater of (a) the sum of Secured Party's Exposure for that
            Valuation Date plus the Notional Volatility Buffer and (b) zero.

            "Notional Volatility Buffer" as determined by the Valuation Agent
            for any date, means the outstanding Notional Amount of the
            Transaction on such date multiplied by the relevant percentage for
            such date as set out in the table below on such date.

                                       Less than or
                                       equal to 5          Less than or equal to
                                       years to            10 years but greater
                                       Termination         than 5 years to
            Party A S&P Rating on      Date of the         Termination Date of
            such date                  Transaction         the Transaction
            ---------------------     -------------        --------------------

            Short Term Rating of            3.25%             4.00%
            A-2

            Short Term Rating of            4.00%             5.00%
            A-3

            Long Term Rating of             4.50%             5.75%
            BB+ or lower

<PAGE>

      IN WITNESS WHEREOF, the parties have executed this Annex by their duly
authorized representatives as of the date of the Agreement.

         BARCLAYS BANK PLC             WELLS FARGO BANK, N.A., not individually
                                       but solely as master servicer under the
                                       Pooling and Servicing Agreement on
                                       behalf of Wells Fargo Alternative Loan
                                       2007-PA1 Trust

By:  /s/ Shain Kalmanowitz               By:  /s/ Carla S. Walker
    -----------------------                  -----------------------------------
    Name:  Shain Kalmanowitz                 Name: Carla S. Walker
    Title: Authorized Signatory              Title:  Vice President
    Date:  February 27, 2007                 Date:  February 27, 2007