The ratio of the number of cups of yellow paint to the number of cups of blue paint that Greg mixed to make a shade of green paint is 2:1. Part A: Write a sentence to describe the number of cups of yellow paint that Greg mixed with each cup of blue paint.

Part B: How many cups of blue paint should Greg add to each cup of yellow paint to make the shade of green? Explain your reasoning.

Part C: If Greg purchased 6 cups of yellow paint for $54, what is the unit price per cup of yellow paint?