A man stands on a platform that is rotating (without friction) with an angular speed of \( 1.2 \...

A man stands on a platform that is rotating (without friction) with an angular speed of \( 1.2 \mathrm{rev} / \mathrm{s} \); his arms are outstretched and he holds a brick in each hand. The rotational inertia of the system consisting of the man, bricks, and platform about the central vertical axis of the platform is \( 6.0 \mathrm{~kg} \cdot \mathrm{m}^{2} \). If by moving the bricks the man decreases the rotational inertia of the system to \( 2.0 \mathrm{~kg} \cdot \mathrm{m}^{2} \), .
What source provided the added kinetic energy?