Consider Holly, a cute little kid. She knows what she likes -- and when it comes to ice cream, made a list of her favorites. At the top is her most favored flavor, and below that is second fav third favorite, and so forth: Ice Cream List . Cookies and Cream . Mint Chocolate Chip . Rocky Road . Rainbow Sherbet Though Holly is young, she still uses marginal analysis to make decisions. So from this list we that Holly will pick Cookies and Cream ice cream today, and her opportunity cost represented as the chance to eat Cookies and Cream