12.2.25 Question Help Find the open intervals on which the function is concave upward or concave downward, and find the location of any points of inflection. f(x) = 2x -4x - 3 Select the correct choice below and fill in any answer boxes within your choice. (Type your answer in interval notation.) O A. The function is concave upward on and concave downward on (Use a comma to separate answers as needed.) O B. The function is concave upward on O C. The function is concave downward on12.2.27 Question Help Find the open intervals where the function f(x) = - 3x* + 27x"+ 168x -5 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. Use a comma to separate answers as needed. Use integers or fractions for any numbers in the expression.) O B. The function does not have an inflection point