a. Why do so many charitable activities like marathons, walks, and 5K runs give the participants “free” T-shirts, wristbands, hats, bumper stickers, and so forth?
b. Charitable organizations could probably make a lot of money for their cause by selling these items on their websites, but you usually have to actually attend the “2012 Cancer Run” to get the “2012 Cancer Run” T-shirt. Why?