While waiting in line to buy two tacos at 75 cents each, and a medium drink for 80 cents, Jordan notices that the restaurant has a value meal containing three tacos and a medium drink all for $2.50. For Jordan, the marginal cost of purchasing the third taco would be
although individuals are at times selfish and at times unselfish, only their selfish actions may be predicted.
people are basically humanitarian, and their actions are, therefore, impossible to predict.
changes in the personal benefits and costs associated with a choice will exert a predictable influence on human behavior.