Solve the following problem:
Problem: An object with a charge of +42 µC is placed at the origin. Another object with a charge of +60 µC is placed a distance of +30 cm from the first object along the x axis. A third object with charge -14 µC is moved from the (x, y) location (0, 10) to (20, 10), where the positions are given in cm. When the third object is moved this distance,
Part A: What is the change in the potential energy?
I know the correct answer but explain how to get this answer for above problem!