Suppose, for some $\theta \in \left[ 0 , \frac { \pi } { 2 } \right] , \frac { \cos 3 \theta } { \cos \theta } = \frac { 1 } { 3 }$. Then $( \cot 3 \theta ) \tan \theta$ equals\\
(A) $\frac { 1 } { 2 }$\\
(B) $\frac { 1 } { 3 }$\\
(C) $\frac { 1 } { 8 }$\\
(D) $\frac { 1 } { 7 }$