a point charge +Q is placed at the origin and a charge -Q is smeared around the origin maintaining cylindrical symmetry around the Z axis.Show that (i) when the charge distribution is prolate(egg-shaped),the monopole and dipole moments are zero but the quadrupole moment Q is positive; (ii) when the charge distribution is oblate(pizza-shaped),the monopole and dipole moments are again zero but the quadrupole moment is negative. please help me solving this problem ....