A ring of radius a = 15.0 cm carries a uniformly distributed positive total charge Q-40.0 C. The electric potential due to the ring at a point P lying a distance x=30.0 cm from its center along the central axis perpendicular to the plane of the ring is a) 8.43 x105 V. b)9.26x105 V c) 1.07x106 V. d) 8.23 x106 V. e) 2.86 x106 V.