The combined mass of the motorcycle and rider is 160 kg. The motorcycle starts from rest at t = 0 and moves along a circular track with a 400-m radius. The tangential component of acceleration of the motorcycle as a function of time is at = 2 + 0.2t m/s^2. The coefficient of static friction between the tires and the track is μs = 0.8. How long after it starts does the motorcycle reach the limits of adhesion (when are its tires on the verge of slipping) and how fast is the motorcycle moving when that occurs?