$(2$pt$)$ Mr$.$ and Mrs$.$ Chan paid $$7000$ for a new central air$-$conditioning unit for thier house. They paid $20\%$ as a down payment and financed the balance with a $36-$month $(3$ year$)$ fixed installment loan with an APR of $5\%$

a$.$ How much was the Chans down payment?

b$.$ How much did the Chans finance?

IiII

c$.$ How much was the Chans monthly payment?

d$.$ How much did the Chans pay in total?

e$.$ What finance charge did the Chans pay?