7. amortization (a) For a student loan of $21,900 at 2.7% for 15 years, Calculate the monthly payment necessary to amortize the loan amount and find the amount of money saved over the lifetime of the loan if an additional $100 is added to the monthly payment. (b) A woman buys a house for $335,000. She pays $20,000 down and takes out a mortgage at 6.9% on the balance. Find her monthly payment and the total amount of interest she will pay if the length of the mortgage is 20 years. (c) Dat charges $15,130 to a credit card with a 18.93% interest rate. If Dat makes a payment of 390.90 each month, how many payments will it take to retire the balance? (d) Large trucks cost $90,000 each. A trucking company buys such a truck and agrees to pay for it by a loan that will be amortized with 10 semiannual payments at 10% compounded semiannually. Complete an amortization schedule for the first four payments of the loan.