4) An athlete dashes past the starting point in a straight-line run at a fairly constant speed of 5 m/s for the first 2 s, and then at 10 m/s for the next 3 s. At that moment she abruptly stops, turns around, waits 1 s, and runs back to the start with a constant speed in 3 s. Draw a graph of the magnitude of her displacement versus time.