While Spinning Down from 500 Rpm to Rest, a Flywheel $3.9 \mathrm {~kJ}$

Multiple Choice

While spinning down from 500 rpm to rest, a flywheel does $3.9 \mathrm {~kJ}$ 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) 4.0 kg
B) 3.4 kg
C) 4.6 kg
D) 5.2 kg