Six particles, each carrying a charge of \(3.0 \mathrm{nC}\), are equally spaced along the equator of a sphere that has a radius of \(0.60 \mathrm{~m}\) and has its center at the origin of a rectangular coordinate system. What is the electrostatic potential (relative to zero at infinity) (a) at the sphere center and \((b)\) at either pole of the sphere?