The Wilson's purchased a home for $$350000.$ The put $25\%$ down and took out a mortgage for the rest. The mortgage had an interest rate of $13\mathrm{.}5\%$ compounded biweekly for an amortization period of $20$ years. At the end of their $7-$year term, the Wilsons renewed their mortgage at $8\mathrm{.}25\%$ compounded biweekly for a $5-$year term and then renewed their mortgage again at $9\mathrm{.}3\%$ compounded biweekly for the remaining $8$ years.

a$)$ What was the monthly payment during the $7-$year term?

b$)$ What was the monthly payment during the $5-$year term?

b$)$ What was the monthly payment during the $8-$year term?

d$)$ How much interest did the Wilsons pay over the $20$ years?