Let f(a) = 23 - 9x3. Find (a) the intervals on which f is increasing, (b) the intervals on which f is decreasing, (c) the open intervals on which f is concave up, (d) the open intervals on which f is concave down, and (e) the x-coordinates of all inflection points. (a) f is increasing on the interval(s) (b) f is decreasing on the interval(s) (c) f is concave up on the open interval(s) (d) f is concave down on the open interval(s) (e) the x coordinate(s) of the points of inflection are 0 Notes: In the first four boxes, your answer should either be a single interval, such as [0, 1), a comma red list of intervals, such as (-inf, 2), (3,4], or the word "none". "none"