Problem 3.24

The electric field strength depends only on the $x$ and $y$ coordinates according to the law $\mathbf{E}=a(x \mathbf{i}+y \mathbf{j}) /\left(x^{2}+y^{2}\right),$ where $a$ is a constant, $\mathbf{i}$ and $\mathbf{j}$ are the unit vectors of the $x$ and $y$ axes. Find the flux of the vector $\mathbf{E}$ through a sphere of radius $R$ with its centre at the origin of coordinates.