Marvin the Martian’s flying saucer is hurtling through space at a rate of 6.8 x 10^7 m/s. In the…

Marvin the Martian’s flying saucer is hurtling through space at a rate of 6.8 x 10^7 m/s. In the span of 20.0 seconds, the flying saucer undergoes a constant (negative) acceleration and has a final velocity of –4.0 x 10^8 m/s. What was the rate of acceleration of the spacecraft? How far did his flying saucer move during a) the entire trip? b) the first 8 seconds?