A student sits on a stool that is free to rotate about a vertical axis. He holds his arms extended horizontally with a 4.0-kg dumbbell in each hand. The instructor starts him rotating with an angular speed of 0.5 rev/s. Assume that friction is negligible and exerts no torque about the vertical axis of rotation. Assume also that the rotational inertia of the student remains constant at 5.0 kgm2 as he pulls his hands to his sides and that the change in rotational inertia is due only to pulling the dumbbells in. Take the original distance of the dumbbells from the axis of rotation to be 90 cm and their final distance 15 cm. Find the final angular speed of the student.