b$)$ If a customer choose to repay $$1700$ monthly for the first three years, and repay $$2000$ monthly after three years. How does your mortgage plan match the customers repay plan? If the customer inquiries about plan change, $($change from plan A to plan B after $3$ years or change from plan B to plan A after $3$ years$),$ How would this affect his payment rate and annuity? Use TVM solver on graphing calculator or online tools to solve these problem. $($C $3\mathrm{.}6)(8$p$)$c$)$ Compare the bonus invest plan offered by each bank. Determine the future value of each plan. Use spreadsheet to solve this problem. Show the detailed formula. $($C$3\mathrm{.}5)(7$p$)$