Instructors Comments: This applet has the ability to help students recognize how the volume of the box (with respect to the length of the cutout) is changing over discrete intervals.  As a teacher, you will want to show one interval at a time asking for student conjectures before each interval.  This is an opportunity to connect the average rates of change to the graphical representation.  Allow the students to make conjectures about the graph before you click each button.