Answer the following questions about the function whose derivative is given below. a. What are the critical points of f? b. On what open intervals is f increasing or decreasing? c. At what points, if any, does f assume local maximum or minimum values? f' (x) = (8 sin x - 8) (2 cos x + 13 ), OsXs 21 . . . a. What are the critical points of f? Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The critical point(s) of f is/are x = (Type an exact answer, using it as needed. Use a comma to separate answers as needed.) O B. The function f has no critical points