A graph titled Speed as a Function of Time with horizontal axis time (seconds) and vertical axis speed (meters per second). A straight orange line labeled A starts at 0 seconds 4 meters per second and runs to 6 seconds 7 meters. A straight blue line labeled B starts at 0 seconds 4 meters and upward to 6 seconds 4 meters. A straight green line starts at 0 seconds 4 meters and runs to 4 seconds 0 meters. Use the graph of speed versus time to answer the questions about acceleration. Which of the cars is speeding up? Which of the cars is slowing down? Which of the cars is maintaining a constant speed?