Exhibit A Underlying Certificates Trust Asset Group Issuer Series Class Issue Date CUSIP Number Interest Rate Interest Type(1) Final Distribution Date Principal Type(1) Original Principal or Notional Balance of Class Underlying Certificate Factor(2) Principal or Notional Balance in the Trust Percentage of Class in Trust Approximate Weighted Average Coupon of Mortgage Loans Approximate Weighted Average Remaining Term to Maturity of Mortgage Loans (in months) Approximate Weighted Average Loan Age of Mortgage Loans (in months) Ginnie Mae I or II 2 Ginnie Mae  2005-013 MA 2/28/2005    38374KUC5 4.25% FIX July 2032 SCH/AD $200,000,000 0.68895533 $82,674,639 60.0000000000% 5.932% 320 33 II 2 Ginnie Mae  2005-013 MI 2/28/2005    38374KUD3 5.50% FIX/IO July 2032 NTL (SCH/AD)    $  27,272,727 0.68895533 $18,789,690 100.0000000000% 5.932% 320 33 II (1)  As defined under "Class Types" in Appendix I to the Base Offering Circular. (2)  Underlying Certificate Factors are as of April 2007. (3)  These Underlying Certificates bear interest during their respective interest accrual periods, subject to the applicable maximum and minimum interest rates, as further described in the related Underlying Certificate Disclosure Documents, excerpts of which are attached as Exhibit B to this Supplement. A-1