A Grindstone of Radius 4

Multiple Choice

A grindstone of radius 4.0 m is initially spinning with an angular speed of 8.0 rad/s. The angular speed is then increased to 12 rad/s over the next 4.0 seconds. Assume that the angular acceleration is constant.
-Through how many revolutions does the grindstone turn during the 4.0-second interval?

A) 0.64
B) 3.8
C) 4.0
D) 6.4
E) 40