A loan is being repaid by 15 annual installments of 1, 000 each. Interest is at an effective rate of 5%. Immediately after the fifth installment is paid, the loan is renegotiated. The revised amortization schedule calls for a sixth payment of 800, a seventh installment of (800 + K), with each subsequent installment increasing by K over the previous payment. The period of the loan is not changed. Determine the revised amount of the last installment.