Monthly 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 loan for the whole amount for the condo for twenty years at 7.0% interest.

a. What is the monthly payment on the mortgage? 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.

b. Then change the amortization to reflect that after ten years, Sherry and Sam will increase their monthly payment to $7,500 per month. 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?