# If $|\bar {a}|=1$,$|\bar {b}|=2$ and the angle between $\bar {a}$ and $\bar {b}$ is $120^{\circ},$ then $\{(\bar {a}+ 3 \bar {b}) \times (3 \bar {a}-\bar {b})\}^2=$

$\begin {array} {1 1} (a)\;425 & \quad (b)\;375 \\ (c)\;325 & \quad (d)\;300 \end {array}$

(d) 300