I can't get this question, can someone give me a hand? I will reprint the question below as it appears in the text: A Solid sphere of radius R has a uniform charge density p(roh) and a total charge Q. Derive an expression for the total electric potential energy.(Suggestion: imagine that the sphere is constructed by adding successive layers of concentric shells of charge dq=[4(pi)r^2 dr)p and use dU=V dq) I tried it a few times but I couldn't come up with a reasonable answer. Any help would be greatly appreciated. Thanks.