Three collars, each of mass m, are connected by pins to bars AC and BC, each of length l and negligible mass. Collars A and B can slide without friction on a horizontal rod and are connected by a spring of constant k. Collar C can slide without friction on a vertical rod, and the system is in equilibrium in the position shown. Knowing that collar C is given a small displacement and released, determine the frequency of the resulting motion of the system.