A car is traveling along a straight road at a velocity of +36.0 m/s when its engine cuts out. For the next twelve seconds the car slows down, and its average acceleration is a̅1. For the next six seconds the car slows down further, and its average acceleration is a̅2. The velocity of the car at the end of the eighteen-second period is +28.0 m/s. The ratio of the average acceleration values is a̅1 / a̅2 = 1.50. Find the velocity of the car at the end of the initial twelve-second interval?