Three charges of magnitude |q| = 3.0 x 10^{-9}C are placed along the circumference of a circle with radius R = 1.0m. A charge +q lies at x = -R, a charge -q at y = -R, and a charge -q at x = R.

a. Determine the electric potential at the origin of the circle.

b. If a negative charge with q = -1.5 x 10^{-9} C brought from r= ∞ and placed at the origin, what is the change in potential energy of the system of charges?