(a) Graph the profit function P(x) = 80x - 0.1x2 - 7000.
(b) Find the vertex of the graph. Is it a maximum point or a minimum point?
(c) Is the average rate of change of this function from x = a < 400 to x = 400 positive or negative?
(d) Is the average rate of change of this function from x = 400 to x = a > 400 positive or negative?
(e) Does the average rate of change of the profit get closer to or farther from 0 when a is closer to 400?