Daniel and his intramural team just won the co$-$ed volleyball tournament, and they$$re celebrating at an all$-$you$-$can$-$eat pizza place. Daniel has had four slices of pizza and is trying to decide whether to have a fifth slice. He does not have to pay for it$,$ but he is thinking about whether feeling overfull from the fifth slice are worth it$.$ Which foundation$($s$)$ of economics is he applying?