A saliboat costs $\$ 30,998$. You pay $10 \%$ down and amortize the rest with equal monthly payments over a 9-year perlod if you must pay $7.8 \%$ compounded monthly, what is your monthly payment? How much interest will you pay? Monthly payments $\$$ (Round to two decimal places.)

Step 1 ：First, calculate the down payment by taking 10% of the total cost of the sailboat. This gives us \(0.1 \times 30998 = \$3099.8\).

Step 2 ：Subtract the down payment from the total cost to find the amount that needs to be amortized: \(30998 - 3099.8 = \$27898.2\).

Step 3 ：Next, calculate the monthly interest rate by dividing the annual interest rate by 12: \(0.078 \div 12 = 0.0065\).

Step 4 ：Calculate the total number of payments by multiplying the number of years by 12: \(9 \times 12 = 108\) payments.

Step 5 ：Use the formula for the monthly payment of an amortizing loan to calculate the monthly payment: \(P = \frac{0.0065 \times 27898.2}{1 - (1 + 0.0065)^{-108}} = \$360.31\).

Step 6 ：Calculate the total amount paid over the 9 years by multiplying the monthly payment by the total number of payments: \(360.31 \times 108 = \$38913.82\).

Step 7 ：Finally, calculate the total interest paid by subtracting the amount that was amortized from the total amount paid: \(38913.82 - 27898.2 = \$11015.62\).

Step 8 ：Final Answer: The monthly payment is approximately \(\boxed{360.31}\) and the total interest paid over the 9 years is approximately \(\boxed{11015.62}\).