In Problems 15-22, find (a) $\mathbf{v} \times \mathbf{w},($ b) $\mathbf{w} \times \mathbf{v}$, (c) $\mathbf{w} \times \mathbf{w}$, and (d) $\mathbf{v} \times \mathbf{v}$.
$$
\begin{aligned}
& \mathbf{v}=2 \mathbf{i}-3 \mathbf{j}+\mathbf{k} \\
& \mathbf{w}=3 \mathbf{i}-2 \mathbf{j}-\mathbf{k}
\end{aligned}
$$