9. Nine years ago a family incurred a 20-year $80,000 mortgage at 8% effective on which they were making annual payments. They desire now to make a lump-sum payment of $50_00 and to pay off the mortgage in nine more years. Find an expression for the revised annual payment a) If the lender is satisfied with an 8% yield for the past nine years but insists on a 9% yield for the next nine years. b) If the lender insists on a 9% yield during the entire life of the mortgage.