Point charges q1, q2, and q3 are fixed at the vertices of an equilateral triangle whose sides are 2.40 m long. Find the electrostatic potential energy of this system of charges for the following charge values.
(a) q1 = q2 = q3 = +4.20 µC
(b) q1 = q2 = +4.20 µC, q3 = -4.20 µC
(c) q1 = q2 = -4.20 µC, q3 = +4.20 µC