A 42.0-cm-diameter wheel, consisting of a rim and six spokes, is constructed from a thin, rigid plastic

Question:

A 42.0-cm-diameter wheel, consisting of a rim and six spokes, is constructed from a thin, rigid plastic material having a linear mass density of 25.0 g/cm. This wheel is released from rest at the top of a bill 58.0 m high.
(a) How fast is it rolling when it reaches the bottom of the bill?
(b) How would your answer change if the linear mass density and the diameter of the wheel were each doubled?