Answer the following questions about the function whose derivative is f'(x) = x(x-4) x% -6. x+6 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 and minimum values? a. What are the critical points of f? Select the correct choice below and fill in the answer box within your choice. A. x= (Use a comma to separate answers as needed) B. The function f has no critical points.