In the given quadratic equation \(3x^2 + 13x + 12 = 0\), we can identify \(A\) and \(C\) as follows:
- \(A = 3\) (the coefficient of \(x^2\))
- \(C = 12\) (the constant term)
Now, we multiply \(A\) and \(C\):
\[ A \times C = 3 \times 12 = 36 \]
So, the correct answer is:
36