Let $a$, $b$, and $c$ be arbitrary nodes in subtrees $\alpha$, $\beta$ and $\gamma$, respectively, in the left tree of Figure 13.2. How do the depths of $a$, $b$, and $c$ change when a left rotation is performed on node $x$ in the figure?
- $b$ retains its depth.
- $a$'s depth is increased by one.
- $c$'s depth is decreased by one.