The graph below shows the altitude, in feet, of a model rocket t seconds after launch. During this time, the rocket experiences three distinct modes of flight. Initially, the engine accelerates the rocket upward. The rocket then coasts upward, is slowed by gravity, and eventually begins to fall. Last, a parachute opens and the rocket drifts smoothly back to the ground. mc030-1.jpg When was the model rocket 600 feet above the ground? 4.5 seconds 7 seconds 7 and 9.5 seconds 4.5 and 12 seconds