Find the intervals in which the function f given by $f (x) = 2x^3 – 3x^2 – 36 x + 7$ is (a) strictly increasing and (b) strictly decreasing ?

Question

This question has appeared in model paper 2012

$\begin{array}{1 1} (A)\; \text{Strictly increasing in }(-2,3) \text{and strictly decreasing in} (-\infty,-2)\; and \;(3,\infty) \\ (B)\; \text{Strictly increasing in} (-\infty,-2) \;and\; (3,\infty)\; \text{and strictly decreasing in} (-2,3) \\ (C)\; \text{Strictly increasing in } (-\infty,-2)\; and\; (-3,2) \text{ and strictly decreasing in} (-2,3) \\ (D) \text{None of the above. } \end{array} $