A teenager pushes tangentially on a small hand-driven merry-go-around and is able to accelerate it from rest to a frequency of 15 rpm in 10.0 s. Assume the merry-go-round is a uniform disk of radius 2.5 m and has a mass of 760 kg, and two children (each with a mass of 25 kg) sit opposite each other on the edge. Upon reaching 15rpm, the teenager stops pushing. Both children walk radially inward to the center of the merry-go-round. Determine the final rotational velocity of the merry-go-round system and the net work performed by the children. also calculate the angular displacement.