Answer:
(a) 
(b) 
Explanation:
Given data
The angular velocity of two cylinders ω=257 rad/s
The mass of the two cylinders m=2.88 kg
The radius of small cylinder r₁=0.319 m
The radius of larger cylinder r₂=0.605 m
For Part (a)
The rotational kinetic energy of the cylinder is given by:

Where I is rotational of inertia of solid cylinder about its central axis.
So

Substitute the given values
So

For Part (b)

Substitute the given values

Volume doesn't depend on what the substance is, only on how much of it there is.