Cars are designed to decelerate passengers over a certain distance. This allows part of the impact to be absorbed in case of a collision. A crash test dummy is in a car traveling at an initial velocity of 21 m/s. The car slams into a brick wall, bringing it to rest at a constant rate of deceleration. If the time between the moment of impact and the moment the crash test dummy comes to rest is 0.3 seconds, how far has the crash test dummy traveled in this time?