The graph models the height of the end of a blade of a windmill as a function of time. A graph has time in seconds on the x-axis and height in feet on the y-axis. A curve starts at (0, 20) and increases to y = 24. It then decreases to y = 15 at 19 seconds. It begins to increase again at 21 seconds. Assume the blade is pointing to the right when t = 0 and that the windmill turns counterclockwise at a constant rate. Use the graph to complete the statements. The blades of the windmill turn on an axis that is feet from the ground.