A rocket (initially at rest) was launched vertically from the ground with a constant acceleration that lasted for 15 seconds. After this the rocket engine stops and the rocket continues to go up freely. After a passage of 22 seconds since the launch, the altitude of the rocket is 5,431 meters from the ground. What was the rockets original acceleration during the first 16 seconds of the flight? Use g = 9.8 m s − 2 , and ignore air resistance.