Free Coffee Refills

Rodin, Harrison, and Harnwell all have student-run convenience stores in their upper mezzanines. The buildings are identical, but the stores are certainly not! While Harnwell has the nicest looking store, Rodin has the cheapest coffee. How can this be if they all charge $1 for a 12oz cup? While Harnwell has a "Buy 10, get the 11th Free" perk card, the Rodin has a "Buy 5, get the 6th Free" perk card. You do not need to be a resident.

Let's say that you want to get caffeinated once a day, five days a week for a semester. The 70 cups of coffee would cost you $59 at Rodin or $64 at Harnwell. You get 11 free cups vs 6. Sure, it's only a difference of $5, but it sure feels nice to get free stuff!