A Thin,massless String Is Wrapped Around a 0

Multiple Choice

A thin,massless string is wrapped around a 0.25m radius grindstone supported by bearings that produce negligible frictional torque.A steady tension of 20 N in the string causes the grindstone to move from rest to a speed of 60 rad/s in 12s.The moment of inertia of the grindstone is

A) 1.0 kg · m²
B) 2.0 kg · m²
C) 3.0 kg · m²
D) 4.0 kg · m²
E) 5.0 kg · m²