Using a Graph to Find the Constant of Proportionality
A graph titled Cost of Tires has Number of Tires on the x-axis and Price of Tires on the y-axis. 2 tires are 80 dollars, 4 tires are 160 dollars, 6 tires are 240 dollars, 8 tires are 320 dollars.

This graph shows a proportional relationship.
What is the constant of proportionality