Need help with b

4. Buster Poindexter and his wife Fifi have decided to purchase a new home in beautiful rural Virginia. The cost of the home is $275,000 and the fifteen- year loan requires a 20% down payment. The mortgage company offers the Poindexter's a variable rate mortgage at 4% APR for the first four years of the loan, 6% APR for years five through ten, and 8% APR for the remaining years. Assume interest is compounded monthly. a. Compute the monthly payment that Fifi will have to pay for the first four years of the loan, the monthly payment for years five through ten and for the years eleven through fifteen. b. Compute the effective monthly interest rate being charged over the fifteen year period. Compute the effective interest rate per year for the variable rate mortgage. You may use Excel to compute these interest rates