12.31: Three particles with chargesQ, Q and
4t7k oo/n ba*q $Q_2$ are initially at rest very (infinitely) far apart from one another. The particles are moved to the locations shown in the figure where they are fixed in place. The particles on the left and right have charge Q and are separated by a distance R. The particle with charge $Q_2$ is located at the midpoint directly between the other charged particles. The total work required to configure this three-particle arrangement is 0. Ignore any self-energies for the particles. What is the value of the charge $Q_2$ ?