The graph shows the amount of money paid when purchasing bags of caramel corn at the zoo: A graph is shown. The x-axis is labeled from 0 to 9. The y-axis is labeled from 0 to 10. The four points shown on the graph are ordered pairs 0, 0 and 1, 3 and 2, 6 and 3, 9. These points are joined by a line. The label on the x-axis is Bags of caramel corn. The title on the y-axis is Total cost in dollars. What is the constant of proportionality? Answers are: 3 , one-third , 2 , or one-half