Any help would be greatly appreciated. This has to do with electric potential, capacitance and electric fields.

A hollow spherical surface of radius a with uniform charge density o is surrounded by another spherical shell of radius 2a having the same centre and an equal, but opposite, amount of charge spread uniformly over its surface. Given: the electric field is zero everywhere, except between the shells where it is (a) Calculate the potential difference between the two spherical surfaces and hence obtain the capacitance of the system. (b) Integrate the electrostatic energy density u . = s by over all space to determine the energy of the system. (c) Calculate U - -C(AV ) and compare your answer to the result from (b)