Two Identical Particles, Each with Charge Q, Are Placed on the X

Multiple Choice

Two identical particles, each with charge q, are placed on the x axis, one at the origin and the other at x = 5 cm. A third particle, with charge -q, is placed on the x axis so the potential energy of the three-particle system is the same as the potential energy at infinite separation. Its x coordinate is:

A) 13 cm
B) 2.5 cm
C) 7.5 cm
D) 10 cm
E) -5 cm