month. they apply all the extra dollars above the original payment to the principal? a. What is the monthly payment on the mortgage? The monthly interest rate on the mortgage is j. (Round to seven decimal places.) The monthly payment on the mortgage is ? (Round to the nearest cent.) Construct the amortization of the loan for the twenty years in a spreadsheet to show the interest cost, the principal reduction, and the ending balance each month. Complete the amortization schedule below to show the interest cost, the principal reduction, and the ending balance for month 125 of the loan: (Round to the nearest cent.)