Solve the given problem:
Problem: The tires of a car make 66 revolutions as the car reduces its speed uniformly from 86km/h to 31km/h . The tires have a diameter of 0.81m.
Part A: What was the angular acceleration of the tires?
Part B: If the car continues to decelerate at this rate, how much more time is required for it to stop?
Please use as much detail as possible in your solution and express your answer using two significant figures.