ALA Menu 1 Task 5 This graph, which is called a step function*, shows how the number of passengers on an airport express van changes over time. The graph shows a trip between a city and the airport. *Note that the endpoints of the steps are either open or closed. The open circles are there to show where the step ends, but are not part of the graph. Why is this characteristic important in order for the graph to represent a function? (a) Write a description of what is shown by this graph. (b) What does the long horizontal line segment on the graph represent