$28.$ A solid sphere of radius R rotates about a diameter with an angular speed w$.$ The sphere then collapses under the action of internal forces to a final radius R$/2.$ What is the final angular speed of the sphere?Hint: Moment of inertia of solid sphere with axis of rotation through center of sphereAlso use principle of conservation of angular momentumA$)$ w$/4$B$)0/2$C$)$D$)20$E$)400$