19.) a plane that carries mail makes a round trip each day from chicago to new york. it makes 2 intermediate stops on the way to new york and 1 intermediate stop on the way back to chicago. suppose you make a graph of the altitude of the plane for one day, with time on the horizontal axis and altitude on the vertical axis. how many times will the graph touch the horizontal axis?

a.) 5

b.) 6

c.) 9

d.) 3