Compute each part of given question:
Question: A conducting sphere of radius a is surrounded by a concentric conducting spherical shell of radius r. The inner sphere carries a charge -Q while the outer shell carries a charge +Q.
Part A: Find the electrostatic field energy contained in the region between the two spherical surfaces by integrating the electrostatic energy over this region.
Part B: Find the force as a function of r between the two shells when the inner sphere is held constant and the radius of the outer sphere is expanded.
Any help I can get on this question is greatly appreciated! I'm not too familiar with this question.