please help!

The interest rate for the first four years of an $99,000 mortgage loan is 9.3% compounded semiannually. Monthly payments are calculated using a 25-year amortization. a. What will be the principal balance at the end of the four-year term? (Do not round intermediate calculations and round your final answer to 2 decimal places.) Principal balance $ b. What will be the monthly payments if the loan is renewed at 6.7% compounded semiannually (and the original amortization period is continued)? (Do not round intermediate calculations and round your final answer to 2 decimal places.) Payment $ per month