Let the mass of the body be $m$
$m=0.5 \mathrm{~kg}$
Velocity of the body is represented by $v=a x^{3 / 2}$
where,
$a=5 \mathrm{~m}^{-1 / 2} \mathrm{~s}^{-1}$.
Initial velocity at $x=0$ will be $v_{1}=a \times 0=0$
Final velocity at $x=2$ will be $v_{2}=a(2)^{3 / 2}=5 \times(2)^{3 / 2}$
Work done by the system=increase in K.E of the body
$=1 / 2 m\left(v_{2}^{2}-v_{1}^{2}\right)=1 / 2 \times 0.5\left[\left(5 \times(2)^{3 / 2}\right)^{2}-0\right]$
$=(1 / 2) \times 0.5 \times(25 \times 8)=50J$