Three vectors extending from the origin are given as $\mathbf{r}_{1}=(7,3,-2)$, $\mathbf{r}_{2}=(-2,7,-3)$, and $\mathbf{r}_{3}=(0,2,3)$. Find $(a)$ a unit vector perpendicular to both $\mathbf{r}_{1}$ and $\mathbf{r}_{2} ;(b)$ a unit vector perpendicular to the vectors $\mathbf{r}_{1}-\mathbf{r}_{2}$ and $\mathbf{r}_{2}-\mathbf{r}_{3} ;$ (c) the area of the triangle defined by $\mathbf{r}_{1}$ and $\mathbf{r}_{2} ;(d)$ the area of the triangle defined by the heads of $\mathbf{r}_{1}, \mathbf{r}_{2}$, and $\mathbf{r}_{3}$.