The graph shows the amount of money paid when purchasing bags of peanuts at the zoo:

A graph is shown. The x-axis is labeled from 0 to 9 and the y-axis is labeled from 0 to 13. The four points shown on the graph are ordered pairs 0, 0 and 1, 4 and 2, 8 and 3, 12. These points are joined by a line. The label on the x-axis is Bags of peanuts. The title on the y-axis is Total cost in dollars.

What is the constant of proportionality? (4 points)

Group of answer choices

4

one-fourth

1

one-third