$L$ is line of intersection of the planes $2x+3y+z=1\:\:and\:\:x+3y+2z=2$ and $\alpha$ is the angle made by the line $L$ with positive $x-axis$ then $cos\alpha=?$

Question

$\begin{array}{1 1} (a)\:\:\large\frac{1}{2}\:\:\:\qquad\:\:(b)\:\:1\:\:\:\qquad\:\:(c)\:\:\frac{1}{\sqrt 2}\:\:\qquad\:\:(d)\frac{1}{\sqrt 3}. \end{array}$</p