For the function below, find a) the critical numbers; b) the open intervals where the function is increasing and e) the open intervals where it is decreasing f(x) = 12x - 9x - 108x + 4 a) Find 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) isare (Type an integer or a simplified traction. Use a comma to separate answers as needed) OB. There are no critical numbers