In economics, total utility refers to the total satisfaction from consuming some commodity. According to the economist Samuelson:14 As you consume more of the same good, the total (psychological) utility increases. However, . . . with successive new units of the good, your total utility will grow at a slower and slower rate because of a fundamental tendency for your psychological ability to appreciate more of the good to become less keen.
(a) Sketch the total utility as a function of the number of units consumed.
(b) In terms of derivatives, what is Samuelson saying?