Celeste Nossiter borrowed $\$ 7400$ from her father to buy a used car. She repaid him after 5 months, at an annual interest rate of $3.9 \%$. Find the total amount she repaid. How much of this amount is interest? The total amount she repaid is $\$ \square$. Of this amount, $\$ \square$ of it is interest. (Round to the nearest cent as needed.)

Step 1 ：Celeste Nossiter borrowed $7400 from her father to buy a used car. She repaid him after 5 months, at an annual interest rate of 3.9%. We are asked to find the total amount she repaid and how much of this amount is interest.

Step 2 ：We can use the formula for simple interest to calculate the total amount Celeste repaid. The formula is \(PRT/100\), where P is the principal amount (the initial amount borrowed), R is the rate of interest, and T is the time period. In this case, P = $7400, R = 3.9%, and T = 5/12 years (since the time period is given in months, we need to convert it to years by dividing by 12).

Step 3 ：Substituting the given values into the formula, we get \(7400 * 3.9 * 0.4166666666666667 / 100\), which gives us the interest amount.

Step 4 ：The interest amount comes out to be $120.25. The total amount repaid is then the sum of the principal amount and the interest, which is \(7400 + 120.25\).

Step 5 ：The total amount she repaid is \(\boxed{7520.25}\). Of this amount, \(\boxed{120.25}\) of it is interest.