Three identical point particles that have charge q are at the vertices of an equilateral triangle that is circumscribed by a circle of radius a that lies in the z = 0 plane and is centered at the origin. The values of q and a are +3.0 µC and 60 cm, respectively. (Assume the potential is zero very far from all charges.) (a) What is the electric potential at the origin? (b) What is the electric potential at the point on the z axis at z = a?