Erin purchased a house for $325,000. He made a downpayment of 15% of the value of the house and received a mortgage for the rest of the amount at 4.50% compounded semi-annually for 20 years. The interest rate was fixed for a 5-year term.

a. Calculate the size of the monthly payments.

b. Calculate the principal balance at the end of the 5-year term.

c. Calculate the size of the monthly payments if after the first 5-year term the mortgage was renewed for another 5-year term at 4.25% compounded semi-annually?