A Charge of 100 NC Resides on the Surface of a Spherical

A charge of 100 nC resides on the surface of a spherical shell of radius 20 cm. The electric potential at a distance of 50 cm from the center of the spherical shell is

A) 18 V
B) 180 V
C) 1800 V
D) 18,000 V
E) None of these is correct.