A train is traveling south when the brakes are applied. It slows down with constant acceleration to a speed of 6.00 m/s in a time of 9.00 s. What is the acceleration of the train during the 9.00-s interval if the train was traveling at 22.4 m/s? If the acceleration is toward north, enter a positive value. If the acceleration is toward south, enter a negative value. m/s 2