Chapter 3.3, Problem 1PP

Let S be the parallelogram determined by the vectors b₁ = $\left[\begin{array}{c}1\\ 3\end{array}\right]$ and b₂ = $\left[\begin{array}{c}5\\ 1\end{array}\right]$, and let A = $\left[\begin{array}{cc}1& -1\\ 0& 2\end{array}\right]$. Compute the area of the image of S under the mapping x ↦ AX.