Question

There are 7 charges, each with q = -5 nC distributed on a circle with radius R=3cm. The center of the circle is at the origin. The charges are at angles 0o, 45o, 90o, 135o, 180o, -90o, and -45o. (Note: A charge at -135o is missing.) a) What is the net electric field at the origin? b) Calculate the electric potential at the origin with respect to infinity.