Exercise 6.4.8

Let $T$ be a linear transformation and suppose $T\left(\left[\begin{array}{r}1\\ -4\end{array}\right]\right)=\left[\begin{array}{r}2\\ -3\end{array}\right]$. Suppose $S$ is the linear transformation with matrix $B=\left[\begin{array}{rr}1&2\\ -1&3\end{array}\right]$. Find $(S\circ T)(\mathbf{v})$ for $\mathbf{v}=\left[\begin{array}{r}1\\ -4\end{array}\right]$.