For the function below, find a) the critical numbers; b) the open intervals where the function is increasing; and c) the open intervals where it is decreasing. f(x) = (x+7)6/7 a) Select the correct choice below and fill in any answer boxes in your choice. OA. The critical number(s) is/are (Type an integer or a simplified fraction. Use a comma to separate answers as needed.). OB. There is no critical number. b) Select the correct choice below and fill in any answer boxes in your choice. O A. List any interval(s) on which the function is increasing. (Type your answer in interval notation. Simplify your answer. Use integers or fractions for any numbers in the expression. Use a comma to separate answers as needed.) OB. The function is never increasing. c) Select the correct choice below and fill in any answer boxes in your choice. OA. List any interval(s) on which the function is decreasing. (Type your answer in interval notation. Simplify your answer. Use integers or fractions for any numbers in the expression. Use a comma to separate answers as needed.) OB. The function is never decreasing.