Answer: $W = \large\frac{1}{2}$$ma^2d$

Work done due to a constant force $W = Fd$.

Constant Force = mass $\times$ acceleration.

Acceleration is given by $ \large\frac{dv}{dt}$$ = \large\frac{dv}{dx}$$ \large\frac{dx}{dt}$

$\Rightarrow = \large\frac{dv}{dt}$$ = \large\frac{a}{2\sqrt {x}}$$a \sqrt{x}$$ = \large\frac{1}{2}$$a^2$

$\Rightarrow W = \large\frac{1}{2}$$ma^2d$