A point charge q is located in vacuum at a distance l from the plane surface, of

Question:

A point charge q is located in vacuum at a distance l from the plane surface, of a uniform isotropic dielectric filling up all the half-space. The permittivity of the dielectric equals e. Find:
(a) The surface density of the bound charges as a function of distance r from the point charge q; analyze the obtained result at l → 0;
(b) The total bound charge on the surface of the dielectric.