A light horizontal rod of negligible mass is mounted on a vertical, frictionless axle and rotates freely with an initial angular speed. Two identical small beads, each of mass \(m\), are initially positioned at equal distances from the axle and then released so that they slide outward along the rod without friction. As the beads move outward, no external torques act on the rod-bead system. Which of the following best describes the shape of the graph of the system's rotational kinetic energy as a function of the beads' distance \(r\) from the axle?