A point charge \(q\) is located at the centre of a ball made of uniform isotropic dielectric with permittivity \(\varepsilon .\) Find the polarization \(\mathbf{P}\) as a function of the radius vector \(\mathbf{r}\) relative to the centre of the system, as well as the charge \(q^{\prime}\) inside a sphere whose radius is less than the radius of the ball.