Topic : angular momentum in case of rotations about a fixed axis

A solid cylinder of mass 20 kg and radius 10 cm rotates about its axis with angular velocity 10 rad/s. The angular momentum of the cylinder about its axis is

The Sun rotates around its centre once in 27 days. What will be the period of revolution if the Sun were to expand to twice its present radius without any external influence? Assume the Sun to be a sphere of uniform density.