This question: 2 point(s Find the open intervals where the function f(x) = - 3x+ 18x + 168x -9 is concave upward or concave downward. Find any inflection points. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The function has a point of inflection at (Type an ordered pair using integers or fractions. Simplify your answer. Use a comma to separate answers as needed.) O B. The function does not have an inflection point. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The function is concave upward on the interval(s). (Type your answer in interval notation. Use integers or fractions for any numbers in the expression. Simplify your answer. Use a comma to separate answers as needed.) O B. The function is never concave upward. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The function is concave downward on the interval(s). (Type your answer in interval notation. Use integers or fractions for any numbers in the expression. Simplify your answer. Use a comma to separate answers as needed.) O B. The function is never concave downward