The function f(x)equals x e Superscript negative x is positive and negative on the interval [negative 1 ,2 ]. 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 nequals 4. c. Use the sketch in part (a) to show which intervals of [negative 1 ,2] make positive and negative contributions to the net area