9. Let f(x) = In x and consider the interval [1, 3]. a. Approximate the area under f (x) using left endpoints with 4 rectangles. b. Approximate the area under f (x) using right endpoints with 4 rectangles. 10. Let f(x) = Vx and consider the interval [2, 8]. a. Approximate the area under f(x) using left endpoints with 6 rectangles. b. Approximate the area under f (x) using right endpoints with 6 rectangles