A machinist turns the power on to a grinding wheel, at rest, at time t = 0 s. The wheel accelerates uniformly for 10 s and reaches the operating angular velocity of 83 rad/s. The wheel is run at that angular velocity for 29 s and then power is shut off. The wheel slows down uniformly at 2.8 rad/s^2 until the wheel stops. In this situation, the time interval of deceleration is closest to: