Sally is selling sandwiches at the beach. If she charges too low of a price, she doesn't make much profit. If she charges too high of a price, she doesn't make many sales, so she doesn't make much profit. In between is the perfect balance when she makes the most profit possible. Below are various prices she has tried charging for a day along with how much profit she made that day. Use a graphing calculator to determine a quadratic model of profit as a function of price.