While Spinning Down from 500 Rpm to Rest, a Flywheel

Multiple Choice

While spinning down from 500 rpm to rest, a flywheel does 3.9 kJ of work. This flywheel is in the shape of a solid uniform disk of radius 1.2 m. What is the mass of this flywheel?

A) 5.2 kg
B) 4.0 kg
C) 3.4 kg
D) 4.6 kg