Amortization schedule. Sherry and Sam want to purchase a condo at the coast. They will spend $650,000 on the condo and are taking out a $650,000 loan for the condo for twenty years at 7.0% interest. What is the annual payment on the mortgage? Construct the amortization schedule of the loan for the twenty years in a spreadsheet to show the annual interest costs, the principal reduction, and the ending balance each year. Then change the amortization schedule to reflect that after ten years Sherry and Sam will increase their annual payment to $80,000 per year. When will they fully repay the mortgage with this increased payment if they apply all the extra dollars above the original payment to the principal?