Solve the equation: $\sin^{-1}(6x) + \sin^{-1}(6\sqrt 3 x) =-\large \frac{\pi}{2}$

Question

(A) $x=-\large\frac{1}{2}$ (B) $x=\large\frac{1}{12}$ (C) $x=-\large\frac{1}{6}$ (D) $x=-\large\frac{1}{12}$