The ratio of the number of cups of blue paint to the number of cups of red paint that Lara mixed to make a shade of purple paint is 3:1. Part A: Write a sentence to describe the number of cups of blue paint that Lara mixed with each cup of red paint.

Part B: How many cups of red paint should Lara add to each cup of blue paint to make the shade of purple? Explain your reasoning.

Part C: If Lara purchased 6 cups of blue paint for $48, what is the unit price per cup of blue paint?