The coffee shop near the local college normally sells 10 ounces of roasted coffee beans for $10. But the shop sometimes puts the beans on sale. During some sales, it offer “33 percent more for free”. Other weeks, it takes “33 percent off” the normal price. After reviewing the shop’s sales date, the shop’s manager finds that “33 percent more for free” sells a lot more coffee than “33 percent off.” Are the store’s customers making a systematic error? Which is actually the better deal?