Comment: This is not an easy exercise, but don’t let the surface mess of the picture put you off. The purpose of the exercise is to challenge you to think hard about very important issues in a new way and at the same time to challenge you to become more skillful at connecting graphs with ideas. We hope you won’t give up and that you’ll feel that what you learn from the time you spend is worth it. Give it a shot, see how far you can get, and if you get stuck, skip to the five exercises that come after the graphs, do those, and then come back to this one.