5. (a) Estimate the area under the graph of f(x) = 1 + x from = x= -1 to x 2 using three rectangles and right end- points. Then improve your estimate by using six rect- angles. Sketch the curve and the approximating rectangles. (b) Repeat part (a) using left endpoints. (c) Repeat part (a) using midpoints. (d) From your sketches in parts (a)-(c), which estimate appears to be the most accurate?