A family has a $ 113,739 25-year mortgage at 5.4 % compounded monthly. (A) Find the monthly payment and the total interest paid. (B) Suppose the family decides to add an extra $100 to its mortgage payment each month starting with the very first payment. How long will it take the family to pay off the mortgage? How much interest will the family save? (A) Monthly payment: $ nothing (Round to two decimal places.)