Find the intervals on which the graph of f is concave upward, the intervals on which the graph of f is concave downward, and the inflection points. f(x) = -x8 +18x5 - 18x + 3 For what interval(s) of x is the graph of f concave upward? Select the correct choice below and, if necessary, fill in the answer box to complete your choic O A. (Type your answer in interval notation. Type an exact answer. Use a comma to separate answers as needed.) O B. The graph is never concave upward. For what interval(s) of x is the graph of f concave downward? Select the correct choice below and, if necessary, fill in the answer box to complete your choi OA. (Type your answer in interval notation. Type an exact answer. Use a comma to separate answers as needed.) B. The graph is never concave downward. Determine the x coordinates of any inflection points of the graph of f(x). Select the correct choice below and, if necessary, fill in the answer box to complete y O A. X= (Type an exact answer. Use a comma to separate answers as needed.) O B. There are no inflection points