A flywheel turns through 40 rev as it slows from an angular speed of 1.5 rad/s to a stop

A flywheel turns through 40 rev as it slows from an angular speed of 1.5 rad/s to a stop.
a) Assuming a constant angular acceleration, find the time for it to come to rest.
b) What is its angular acceleration?
c) How much time is required for it to complete the first 20 of the 40 revolutions?