The graph shows the cost of renting a bicycle. A graph with small horizontal steps showing hours rented on the x axis and rental cost in dollars on the y axis. The steps have open dots on the left ends and closed dots on the right ends. From left to right the dots are open zero comma 4 and closed 1 comma 4, then open 1 comma 6 and closed 2 comma 6, then open 2 comma 8 and closed 3 comma 8, then open 3 comma 10 and closed 4 comma 10, then open 4 comma 12 and closed 5 comma 12, then open 5 comma 14 and closed 6 comma 14.

For this function, what is the average rate of change over the interval 5.5 ≤ x ≤ 6?
A. 3
B. 1
C. 0.5
D. 0