This chart represents a variety of student counts and the income created by each. The chart illustrates school income increasing to 200 students and decreasing after 250 students. At the extreme values of the chart, 0 and 450 students, the school income is 0. Therefore, there is a maximum income value for the school on the closed interval [0, 450]. At closer inspection, the maximum income will within the closed interval of [200, 250].