Joe buys a house for a purchase price of $125,000 with a down payment of 20% and uses a mortgage to finance the remainder. (a) How much is the original amount of Joe's mortgage? (b) Assuming that Joe has a 25-year mortgage at 5.54% compounded monthly, find the monthly payment. What formula did you use? (c) How much does Joe pay in interest over the total 25 years of the mortgage? Explain. (d) What is the unpaid balance after 5 years? Explain and show your work