The work done on a particle of mass m by a force, $$K \left[\frac {x}{\left(x^2 + y^2\right)^{\frac{3}{2}}}\widehat{i} + \frac {y}{\left(x^2 + y^2\right)^{\frac{3}{2}}}\widehat{j} \right]$$ (K being a constant of appropriate dimensions), when the particle is taken from the point (a, 0) to the point (0, a) along a circular path of radius a about the origin in the x-y plane is

A

$$\frac{2K \pi}{a}$$

B

$$\frac{K \pi}{a}$$

C

$$\frac{K \pi}{2a}$$

D

0