A car is traveling on a straight road with velocity of +36.0m/s when its engine cuts out. For the next 12 seconds the car slows down, and its average acceleration is a1. for the next six seconds the car slows down further, and its average acceleration is a2. the velocity of the car at the end of the eighteen second period is +28.0 m/s. the ratio of the average acceleration value is a1,a2 = 1.50. find the velocity of the car at the end of the initial tweleve-second interval?