The following functions are positive and negative on the given interval.

a. Sketch the function on the given interval.

b. Approximate the net area bounded by the graph of f and the x-axis on the interval using a left, right, and midpoint Riemann sum with n = 4.

c. Use the sketch in part (a) to show which intervals of [a, b] make positive and negative contributions to the net area.

f(x) = 4 - 2x on [0, 4]