A summer cottage, valued at $120,000, may be purchased by paying a $20,000 down payment and financing the balane with a mortgage at 9% compounded semi-annually and monthly payment for 15 years. a) find the monthly payment. Round up to the next dollar. b) How much of the 60th payment pays interest and how much goes to ward the principal? c) After the 100th payment, how mch of the original mortgage is still left to be paid? d) After the making of 115 payments, what percent of the original debt will have been paid off?