If the spring is unstretched when θ = 30°, the mass of the cylinder is 25 kg, and the mech...

If the spring is unstretched when θ = 30°, the mass of the cylinder is 25 kg, and the mechanism is in equilibrium when θ = 45°, determine the stiffness k of the spring. Rod AB slides freely through the collar at A. Neglect the mass of the rods.