If $\alpha$ is a root of $25 \cos^2 \theta + 5 \cos \theta - 12 =0$ $\frac{\pi}{2} < \alpha < \pi$, then $\sin 2 \alpha$ is equal to :

Question

( A ) $-\frac{13}{18}$
( B ) $-\frac{24}{25}$
( C ) $\frac{13}{18}$
( D ) $\frac{24}{25}$