Given $A = \begin{bmatrix} 6 & -3 \\ 2 & 1 \end{bmatrix}$ and $B = \begin{bmatrix} 4 & 1 \\ 0 & -1 \\ 5 & 9 \end{bmatrix}$, find the product AB if possible.
Select the correct choice below and, if necessary, fill in the answer box to complete your choice.
A. AB = (Simplify your answer.)
B. The matrix product does not exist.