Three children are riding on the edge of a merry-go-round that is 150 kg, has a 1.40-m radius, and is spinning at 18.0 rpm. The children have masses of 22.0, 28.0, and 33.0 kg. If the child who has a mass of 28.0 kg moves to the center of the merry-go-round, what is the new angular velocity in rpm?