Unearned Interest by the Actuarial Method Each loan was paid in full before its due date. $($a$)$ Obtain the value of $h$ from Table $5.$ Then $($b$)$ use the actuarial method to find the amount of unearned interest, and $($c$)$ find the payoff amount.

$\backslash$table$[[\backslash$table$[[$Regular$],[$Monthly$],[$Payment$]],$APR,$\backslash$table$[[$Remaining Number of$],[$Scheduled Payments$],[$after Payoff$]]],[$$$346\mathrm{.}70,4\mathrm{.}0\%,18],[$$$783\mathrm{.}50,5\mathrm{.}5\%,12],[$$$595\mathrm{.}80,7\mathrm{.}0\%,6],[$$$314\mathrm{.}50,9\mathrm{.}0\%,24]]$