Two masses are tied to a rope. The first mass is attached to a spring that is then attached to the ground. The rope is then passed over a frictionless pulley so that mass 2 hangs freely, pulling straight up on mass 1, which in turn pulls straight upward on the string. This system is allowed to reach equilibrium. Mass 1 = 2kg, mass 2 = 5kg, and the spring constant k = 300N/m. How much potential energy is stored in the spring?