When a lender suffers a loss on a loan insured hereunder, including accrued interest, a claim therefor shall be submitted to the Secretary. If the Secretary finds that the loss has been suffered, he shall reimburse the lender therefor: Provided, That the amount payable to the lender for a loss on any one loan shall not exceed 90 per centum of such loss: Provided further, That no reimbursement may be made for losses in excess of 15 per centum of the aggregate of insured loans made by the lender: Provided further, That before any reimbursement is made, all reasonable collection efforts shall have been exhausted by the lender, and the security for the loan shall have been liquidated to the extent feasible, and the proceeds applied on the debt. Upon reimbursement, in whole or in part, to the lender, the note or judgment evidencing the debt shall be assigned to the United States, and the lender shall have no further claim against the borrower or the United States. The Secretary shall then take such further collection action as may be warranted, or may cancel the uncollectable portion of any debt assigned pursuant hereto. The Secretary may establish a date upon which accrual of interest or charges shall cease.