In january 2004, nasa landed exploration vehicles on mars. part of the descent consisted of the following stages:
stage a: friction with the atmosphere reduced the speed from 19300 km/h to 1600 km/h in 4.0 min.
stage b: a parachute then opened to slow it down to 321 km/h in 94 s.
stage c: retro rockets then fired to reduce its speed to zero over a distance of 75 m.
assume that each stage followed immediately after the preceding one and that the acceleration during each stage was constant.

1- find the rocket's acceleration (in m/s2) during stage a

2- find the rocket's acceleration (in m/s2) during stage b

3-find the rocket's acceleration (in m/s2) during stage c