4. A disk with a radius of 2.0 m and a rotational inertia of 0.40 kg·m 2 rotates with an angular speed of 4.0 rad/s around a frictionless vertical axle. A wade of clay (m = 25 g) drops onto and sticks to the edge of the disk. What is the new angular speed of the disk? (A) 3.2 rad/s (B) 3.6 rad/s (C) 2.7 rad/s (D) 1.1 rad/s (E) 0.67 rad/s