5. (10%)

$$\text{Let } A = \begin{bmatrix} 0 & 0 & 3 & -4 \\ 2 & -3 & 3 & -3 \\ 0 & 0 & 1 & 2 \\ 1 & 1 & -1 & 1 \end{bmatrix}^T \text{ and } B = \begin{bmatrix} 1 & 2 & -1 & 2 \\ -3 & 4 & 3 & -6 \\ 0 & 0 & 1 & 4 \\ 0 & 0 & 3 & -8 \end{bmatrix} \text{.please find |AB|}.$$