posted by Sean .
a red car and a green car, identical except for the color, move toward each other in adjacent lanes and parallel to an x axis. At time , the red car is at and the green car is at . If the red car has a constant velocity of 20 km/h, the cars pass each other at , and if it has a constant velocity of 40 km/h, they pass each other at . What are (a) the initial velocity and (b) the acceleration of the green car?