Phil, Miriam, Zakee, and Nancy are roommates who share groceries. Phil eats the most, Miriam eats the next most, and Nancy and Zakee eat the least. They all decide that they want to implement a grocery-sharing scheme where everyone agrees to share the cost of food equally.

However, Zakee and Nancy quickly find that they do not get a fare share of food, and drop out of the food sharing scheme. As soon as Zakee and Nancy drop out, Miriamknows that she will also want to drop out.

What concept did Nancy learn about in ConSci2910 that allows her to predict that she will want to drop out?