Find the amount by which the debt increases due to a late payment involving compound interest

Question

Tony owes Peter R9000 due in twelve months from now, earning an interest rate of 15 % per annum compounded monthly

Tony is unable to pay on the due date, and pays sixteen months from now. How much more will he pay?

My attempt:

$$S=P(1+i)^n =9000(1+0,15)^{16} =9000 \times 9.357620874 =54218.58787 $$

Answer 1

Hint: You should divide the annual interest, 0.15, by 12 to get the monthly interest.

Answer 2

The amount owed would have been $9000(1+r)^{12}$ where $r=\frac{0.15}{12}$.

Now it will be $9000(1+r)^{16}$. This number turns out to be the answer A. However, since the problem asks how much more will he pay, I do not consider that to be the correct answer. The actuall difference is about $532.22$.