Final answer:
To find the total cost of the sports coupe including interest, one would normally calculate the monthly payment using an amortization formula, then multiply it by 72 months. However, the specific monthly payment amount has not been provided, so the total cost including interest cannot be determined without it.
Step-by-step explanation:
To calculate the total cost of a new sports coupe, including interest, we need to use the loan information provided ($74,300 loan at an APR of 6.7% for 72 months) to determine the monthly payment and then multiply it by the number of months to get the total cost. The monthly payment can be calculated using the formula for an amortizing loan, which is not provided here, but the output of such a formula would give us the monthly payment required.
Once the monthly payment is calculated, we multiply it by 72 (the number of months for the loan term) to find out the total amount paid over the life of the loan, which includes both the principal and the interest. To get the total cost of the car including interest, we add the down payment (if any) to this amount.
However, without the exact monthly payment amount, we cannot provide the total cost including interest. Normally, you would find the monthly payment using a financial calculator or an amortization formula, and then proceed with the mentioned steps.