The ratio of the number of cups of red paint to the number of cups of yellow paint that Garcia mixed to make a shade of orange paint is 4:1.

Part A: Write a sentence to describe the number of cups of red paint that Garcia mixed with each cup of yellow paint. (4 points)

Part B: How many cups of yellow paint should Garcia add to each cup of red paint to make the shade of orange? Explain your reasoning. (4 points)

Part C: If Garcia purchased 6 cups of red paint for $42, what is the unit price per cup of red paint? (2 points)