How can the relationship between the hours after sunset, x, and the temperature, y, be modeled? If the relationship is modeled with a linear function, describe the correlation between the two data sets.

Mary and roberto bought identical backpacks at different stores. mary's backpack originally cost $65 and was discounted 25%. roberto's backpack originally cost $75 and was on sale for 30% off on the original price. which backpack was the better buy?