Observe the following statements and choose correct answer.
Assertion (A) : A body of mass 3kg moves according to $\mathrm{s}=1+\mathrm{t}+{\mathrm{t}}^2$ $(\mathrm{t}$ in seconds, $\mathrm{s}$ in centimeters$).$ Its kinetic energy when $\mathrm{t}=5\sec$ is $181.5\times {10}^3$ ergs
Reason (R) : Kinetic energy $=\frac{1}{2}{\mathrm{mv}}^2$