PLEASE ANSWER THIS 4 part question

The fastest speeds traveled on land have been achieved by rocket-powered cars. The current speed record for one of these vehicles is about 1090 km/h, which is only 160 km/hr less than the speed of sound in air. Suppose a car that is capable of reaching a speed of 1.09 103 km/hr is tested on a flat, hard surface that is 25.0 km long. The car starts at rest and just reaches a speed of 1.09 103 km/hr when it passes the 20.0 km mark.

i. If the car's acceleration is constant, how long does it take to make the 20.0 km drive? These are positions along a line (like a number line). Practice Worksheet for Linear Motion

ii. How long will it take the car to decelerate if it goes from its maximum speed to rest during the remaining 5.00 km stretch?

iii. If the distance of the stretch it took to stop were doubled, how long would the car take to decelerate?

iv. During an unknown amount of time, a different race car with non-constant acceleration travels from "xi" to "xf", accelerating from "vi" to "vi". In terms of "xi", "xf", "vi", and "vf", what is the magnitude of acceleration which occurred between the two position?