A variable-rate mortgage of $142,000 is amortized over 15 years by equal monthly payments. After 12 months the original interest rate of 6% compounded semi-annually was raised to 8.7% compounded semi-annually. Three years after the mortgage was taken out, it was renewed at the request of the mortgagor at a fixed rate of 7.6% compounded semi-annually for a four-year term. (a) Calculate the mortgage balance after 12 months. (b) Compute the size of the new monthly payment at the 8.7% rate of interest. (c) Determine the mortgage balance at the end of the four-year term