A step (or staircase) function.
These functions are constant in given intervals, and non continuous between one interval and the other.
Assume that the x axis represents the time, in minutes, and the y axis represents the cost in dollars.
The interval [tex] [0,1] [/tex] counts as fraction of a minute or one minute, so the cost is 0.45.
The interval [tex] (1,2] [/tex] counts as fraction of two minutes or two minutes, so the cost is 0.90.
In general, the interval [tex] (n-1, n] [/tex] counts as fraction of [tex] n [/tex] minutes or [tex] n [/tex] minutes, so the cost is [tex] n\cdot 0.45 [/tex]
