American economist Paul Federman always buys donuts for every research contract he gets. Later, he developed the habit of putting a basket of donuts in the office every weekend for everyone to eat. In order to recover the cost He put a basket next to the bread basket with the recommended price. As a result, this unattended collection basket recovered 95% of the bread money. Later, he resigned to sell doughnuts. Every morning, he took the doughnuts and the collection basket. After a few years, Federman made as much money as when he was a research analyst. The most suitable for this text title is:. ['An experiment on honesty.', 'A story of making money by wisdom.', 'Generation of a new sales method.', 'Treating business as an economic experiment.']