The block of mass 2 kg is initially at rest on a horizontal force $\overrightarrow {F}=(9-x^2) \hat i$ newtons acts on it, when the block is at $x=0$. The maximum kinetic energy of the block between $x=0$ and $x=3m$ in joule is :

Question

$$\begin {array} {1 1} (a)\;24 & \quad (b)\;20 \\ (c)\;18 & \quad (d)\;15 \end {array}$$