Note that the maximum doesn't always exist.

Please consider that the maximum doesn't exist in some circumstances.

The price of the picture is 10 pounds.

The end product is worth ten times as much as the materials used.

Even though a parameter's value can change, it is treated as a constant, not as a variable.

China's the only country where three people can eat at a mid-range hotpot buffet for only 5 RMB, but a hamburger costs five times as much. Figure that one out!