6. Two masses 3 m and m are connected by a light inextensible cord passing over a smooth frictionless pulley. The system is at rest with the 3 m mass resting on the ground as shown in the diagram. A third mass m falls through a height of 2.5 m and strikes the mass m on the pulley, adheres to it and sets the whole system in motion. Calculate the height to which the 3 m mass will rise before coming to rest momentarily. 5 m