A 4.0-m-diameter playground merry-go-round, with a moment of inertia of is freely rotati...

A 4.0-m-diameter playground merry-go-round, with a moment of inertia of is freely rotating with an angular velocity of 2.0 rad/s. Ryan, whose mass is 80 kg, runs on the ground around the outer edge of the merry-go-round in the opposite direction to its rotation. Still moving, he jumps directly onto the rim of the merry-go-round, bringing it (and himself) to a halt. How fast was Ryan running when he jumped on?