A solid sphere of radius \(R\) is concentric with a spherical shell that carries charge \(+q_{\text {shell }}\) and has an inner radius of \(2 R\) and outer radius of \(3 R\). If the electrostatic potential at the common center of the sphere and shell is the same as the potential at infinity, what is the charge \(q_{\text {sphere }}\) on the solid sphere \((a)\) if the sphere is conducting and \((b)\) if the sphere is nonconducting and has a uniform charge distribution throughout it?