A new employee charged $\$ 2790$ on his credit card to relocate for his first job. After noticing that the interest rate for his balance was $21 \%$ compounded monthly, he stopped charging on that account. He wishes to pay off his balance in 3 years using automatic payments sent at the end of each month. b. How much total interest will he have paid? a. What monthly payment must he make to pay off the account at the end of 3 years? $\$ 105.11$ (Round to the nearest cent as needed.) b. How much total interest will he have paid? $\$ \square$ (Round to the nearest cent as needed.)

Step 1 ：Given that the present value (PV) of the loan is $2790, the annual interest rate is 21%, and the loan term is 3 years (or 36 months).

Step 2 ：First, we need to convert the annual interest rate to a monthly rate by dividing it by 12. So, the monthly interest rate (r) is \(0.21 / 12 = 0.0175\).

Step 3 ：Next, we use the formula for the monthly payment of a loan, which is given by: \(P = [r*PV] / [1 - (1 + r)^{-n}]\). Substituting the given values, we get the monthly payment (P) as \($105.11\).

Step 4 ：Then, we calculate the total amount paid over the 3 years by multiplying the monthly payment by the total number of payments. So, the total amount paid is \($105.11 * 36 = $3784.08\).

Step 5 ：Finally, we calculate the total interest paid, which is the total amount paid minus the original principal amount. So, the total interest paid is \($3784.08 - $2790 = $994.08\).

Step 6 ：Final Answer: The total interest he will have paid is \(\boxed{994.08}\).