13 a. Find the largest possible open interval(s) on which f is increasing, and the largest possible open interval(s) on which f is decreasing. Select the correct choice below and, if necessary, fill in the answer box(es) within your choice. A. The function is increasing on the open interval(s) (8,12) and decreasing on the open interval(s) (7,8). (Simplify your answer. Type your answer in interval notation. Use a comma to separate answers as needed.) B. The function is decreasing on the open interval(s) . The function is never increasing. (Simplify your answer. Type your answer in interval notation. Use a comma to separate answers as needed.) . The function is never decreasing. C. The function is increasing on the open interval(s) (Simplify your answer. Type your answer in interval notation. Use a comma to separate answers as needed.) D. The function is never increasing nor decreasing. b. Find the critical points of f. Which critical points correspond to local maxima? Local minima? Neither? Find the critical points of f. Select the correct choice below and, if necessary, fill in the answer box within your choice A. The critical point(s) are located at x = 8,10. (Use a comma to separate answers as needed.) B. There are no critical points. Which critical points correspond to local maxima? Select the correct choice below and, if necessary, fill in the answer box(es) within your choice. A. The critical point(s) x = correspond(s) to local maxima. (Use a comma to separate answers as needed.) B. There are no critical points that correspond to local maxima.