The graph below represents the price of sending picture messages using the services of a phone company. What is the constant of proportionality?
A graph is shown. The values on the x axis are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. The values on the y axis are 0, 22, 44, 66, 88, 110, 132, 154, 176, 198, 220. Points are shown on ordered pairs 0, 0 and 2, 44 and 4, 88 and 6, 132 and 8, 176. These points are connected by a line. The label on the x axis is Picture Messages Sent. The label on the y axis is Price in cents.
A. 10
B. 11
C. 21
D. 22