The problem gives us the value for the initial velocity of the race car, and the time it takes for the race car to come to a complete stop. The question however, proves to be tricky. The question states as follow: "what is the acceleration of the car after 12.0 seconds?" Since it was already established that the car has come to a halt in 12.0 seconds, therefore, the acceleration would have to be 0, as the car would not be moving at all.
