Let $\bar {v}=2 \bar{i}+\bar {j}-\bar {k}$ and $\bar {w}=\bar {i}+3 \bar{k}$. If $ \bar u$ is any unit vector then the maximum value of the scalar triple product $(\bar {u} \; \bar {v}\; \bar {w})$ is

Question

\[\begin {array} {1 1} (a)\;1 & \quad (b)\;\sqrt {10}+\sqrt {6} \\ (c)\;\sqrt {59} & \quad (d)\;\sqrt {60} \end {array}\]