Two identical metallic blocks resting on a frictionless horizontal surface are connected by a light metallic spring having a spring constant $k$ as shown in Figure $\mathrm{P} 23.59 \mathrm{a}$ and an unstretched length $L_{i} .$ A total charge $Q$ is slowly placed on the system, causing the spring to stretch to an equilibrium length $L,$ as shown in Figure P23.59b. Determine the value of $Q,$ assuming that all the charge resides on the blocks and modeling the blocks as point charges.
(FIGURE CANNOT COPY)