Find the average potential over a spherical surface of radius $R$ due to a point charge $q$ located inside (same as above, in other words, only with (In this case, of course, Laplace's equation does not hold within the sphere.) Show that, in general,
$$
V_{\text {ave }}=V_{\text {center }}+\frac{Q_{\text {enc }}}{4 \pi \epsilon_{0} R}
$$
where $V_{\text {center }}$ is the potential at the center due to all the external charges, and $Q_{\text {enc is the total }}$ enclosed charge.