Approximate the area under the graph of 2 f(x) and above the xaxis with rectangles, f(x) = + 4, from x = 1 to x = 9 using the following methods with n = 4. x (a) Use left endpoints. (b) Use right endpoints. (0) Average the answers in parts (a) and (b) (C!) Use midpoints. The area, approximated using the left endpoints, is D. (Round to two decimal places as needed.) The area, approximated using the right endpoints, is D. (Round to two decimal places as needed.) The average of the answers in parts (a) and (b) is D. (Round to two decimal places as needed.) The area, approximated using the midpoints, is D. (Round to two decimal places as needed.)