Answer
Purchase of $70$ shirts, for a price of ${{\$}} 20.80$ per shirt.
Work Step by Step
Using the same graphing window in part (a), we cancel the graphs for the cases other than case C.
We estimate that the graph is at its lowest point at $(70,20.8)$, representing the purchase of $70$ shirts, for a price of ${{\$}} 20.80$ per shirt.
