Suppose there are two residents of a duplex (Olivia and Paola) who are considering buying a hot tub to install in their shared patio. They have a proposal for contributions to fund the hot tub. Each resident can choose to contribute $2000 or not contribute at all. The total contributions will be pooled to fund the purchase of the hot tub. Since both residents have access to the shared patio, one resident can not prevent the other resident from using the hot tub, even if she did not contribute to its purchase. If both residents contribute, they can purchase a deluxe hot tub for $4000, and each will receive $3000 worth of benefit from using the hot tub. If neither resident contributes, there will be no hot tub purchased, the benefit here is $0 If one resident contributes, and the other does not, they can purchase an inflatable hot tub for $2000, and each will receive $1500 worth of benefit.