(Mortgage restructuring) An investor purchased a small apartment building for $250,000. She made a down payment of $50,000 and financed the balance with a 30 year, fixed-rate mortgage at 12% annual interest, compounded monthly. For exactly 20 years she has made equal-sized monthly payments as required by the terms of the loan. Now she has the oppor- tunity to restructure the mortgage by refinancing the balance. She could borrow the current balance, pay off the original loan, and assume a new loan for the balance. (No points or any other charges are involved in the transaction.) The new loan is a 20-year, fixed-rate loan at 9% , compounded monthly, to be paid in equal monthly installments. Suppose she has a risk-free savings account that pays 5%, compounded monthly. Should she restructure the mortgage?