A partially amortizing mortgage is made for $60,000 for a term of 10 years. The borrower and lender agree that a balance of $20,000 will remain and be repaid as a lump sum at that time. a) If the interest rate is 7 percent, what must monthly payments be over the 10-year period? b) If the borrower chooses to repay the loan after five years instead of at the end of year 10, what must the loan balance be