If \( \displaystyle \lim_{x \to 0} \frac{\sin^{-1}x - \tan^{-1}x}{3x^3} \) is equal to \( L \), then the value of \( (6L + 1) \) is:
\( \frac{1}{2} \)
\( 2 \)
\( 6 \)
\( \frac{1}{6} \)