Answer: Public good
Explanation: Working for the public good, everyone, including the butcher, takes their own interest and works for it, thus contributing to the interest of the community better than any other promotional activity or activity related to the public good. That is the essence of Smith's Wealth of the People, the highlighting of the individual and their activities in their own interest, then the division of labor, as a precondition for the creation of a rich nation, that is, the common good.