(a) Write an expression for the electric charge density p (r) of a point charge q at r'. Make sure that the volume integral of p equals q.

(b) What is the charge density of an electric dipole, consisting of a point charge – q at the origin and a point charge + q at a?

(c) What is the charge density of a uniform, infinitesimally thin spherical shell of radius R and total charge Q, centered at the origin? [Beware: the integral over all space must equal Q.]