Stephen purchased a house for $425,000. He made a down payment of 15.00% of the value of the house and received a mortgage for the rest of the amount at 6.12% compounded semi-annually amortized over 20 years. The interest rate was fixed for a 3 year period.

a. Calculate the monthly payment amount.

b. Calculate the principal balance at the end of the 3 year term.

c. Calculate the monthly payment amount if the mortgage was renewed for another 3 years at 4.62% compounded semi-annually?