Solve the all parts of following problem:
Problem: Colonel John P. Stapp, USAF, participated in studying whether a jet pilot could survive emergency ejection. On March 19, 1954, he rode a rocket-propelled sled that moved down a track at a speed of 632 mi/h. He and the sled were safely brought to rest in 1.40 s.
Part A: Determine the negative acceleration he experienced.
Part B: Determine the distance he traveled during this negative acceleration.
Don't just give me the answer; explain your steps as well.