(a)[2]
Reflect triangle $A$ in the line $x = 1$. Give the image the label $B$.
(b)[5]
Triangle $A$ is sent to triangle $D$ by two transformations used in sequence. First, triangle $A$ goes to triangle $C$ under transformation $Y$. Next, triangle $C$ goes to triangle $D$ by a translation of $\begin{pmatrix}6\\1\end{pmatrix}$. Describe fully transformation $Y$.