A peach farmer sells baskets of peaches at the local farmers market. He finds that when he charges $10 for each basket, he can sell 80 baskets in one day. He's also notices that for every $2 increase in the price he charges per basket of peaches, the average number of baskets he sells in a day decreases by 2. He determines that he will not sell his peaches for less than $10 a basket or more than $30 a basket. The function in the graph below models the peach farmer's revenue, y, in relation to the price he charges per basket, x.