Find any critical numbers for f and then use the second derivative test to decide whether the critical number(s) lead to relative maxima or relative minima. If f"'(c) = 0 or f' second derivative test gives no information. In this case, use the first derivative test instead. f (x ) = x 15/7 8/7 What is/are the critical number(s)? Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The critical number(s) is/are x = (Simplify your answer. Use a comma to separate answers as needed.) O B. There are no critical numbers. Where are the relative extrema? Select the correct choice below and, if necessary, fill in the answer box(es) to complete your choice. O A. There is a relative maximum at x = . There are no relative minima. (Simplify your answer. Use a comma to separate answers as needed.) O B. There is a relative maximum at x = and a relative minimum at x = (Simplify your answers. Use a comma to separate answers as needed.) O C. There is a relative minimum at x = . There are no relative maxima. (Simplify your answer. Use a comma to separate answers as needed.) O D. There are no relative extrema