Problem 03.02 Electric Potential Energy of Point Charges Three charges q1 = 1.0 nC, q2 = -2.0 nC, and q3 = 3.0 nC are fixed in an equilateral triangle of side length d = 5.0 cm, as shown below. 92 93 K=8.99x10° N m²/C (a) Write down the expression for the potential energy U12 of a system of two charges qi and q2 at a separation distance of 12. (b) What is the electric potential energy of this configuration?