Chapter B, Problem 4E

If $A=\left(\begin{array}{cc}1& 4\\ \begin{array}{l}5\\ 8\end{array}& \begin{array}{l}10\\ 12\end{array}\end{array}\right)$ and $B=\left(\begin{array}{ccc}\begin{array}{l}-4\\ 1\end{array}& \begin{array}{l}6\\ -3\end{array}& \begin{array}{l}-3\\ 2\end{array}\end{array}\right)$, find

(a) AB

(b) BA