show steps to calculation to put in excel!!! As a borrower, you have the option to choose between two $30-$year, monthly$-$payment loans: $7\%$ interest rate with $3$ points, versus $7\mathrm{.}5\%$ interest with one$-$half point.

$($a$)$ Which loan option would you choose if you had a $10-$year expected prepayment horizon?

$($b$)$ Which would you choose if you expect to pay off this loan in $5$ years?