of 80 f(x) dx? You may assume that f(x) is concave down on the interval [0,80]. Based on the following graph of f(x), which one of the following values is a possible value of Hint: Approximate the area of the shaded region using a rectangle and a triangle. 0000 880 1600 400 1120 1000 20 15 10 5 y x 80