Electrostatics - Hard

The intensity of an electric field depends only on the coordinates

x

y

and

z

as follows:

\vec{E} = \dfrac{\alpha\,(x\hat{i} + y\hat{j} + z\hat{k})}{(x^2 + y^2 + z^2)^{3/2}}

The electrostatic energy stored between two imaginary concentric spherical shells of radii

R

and

2R

with centre at the origin is