The annual card of the gym is told by the service staff, so all items can be used for one year, unlimited time and unlimited times. However, our time cost is limited. We went a lot in the first month or two, even if it was cheap, it wouldn't last a year. This calculation is uneconomical. The money they earn, you may not go for a year.

To sum up: marginal utility refers to the extra satisfaction you get for every extra commodity you consume.

N a variety of thinking modes to help you make progress every day.