Squeezing Range

If $f(x) = x^3 - 2x^2 \sin \theta + x + 1 \; (0 \leq \theta \leq \pi)$ has both a local maximum and a local minimum, the range of $\theta$ can be restricted further by $a \pi < \theta < b \pi$ . What is the value of $30(b-a)?$