Say you belong to a group that has 20 members (N), and in order to get a particular
benefit (B) you need 12 members (K) to contribute. This benefit (B) is a public good,
which means that you will get to enjoy it whether you contribute or not. Assume that
those who contribute to the provision of the benefit pay a cost, C. Of course, B > C.
If you know that exactly 10 members of the group (aside from yourself) will
contribute, what should you do?