Determine which of the following linear functions $L: \mathbb{R}^2 \rightarrow \mathbb{R}^2$ has an inverse, and, if so, describe it: (a) the scaling transformation that doubles the length of each vector; (b) clockwise rotation by $45^{\circ}$; (c) reflection through the $y$-axis; (d) orthogonal projection onto the line $y=x$; (e) the shearing transformation defined by the matrix $\left(\begin{array}{ll}1 & 2 \\ 0 & 1\end{array}\right)$.