5. Let f(x) = 18x5/3 -9p5/3. Use exact values for each. (a) On what interval(s) is f increasing or decreasing? (6 pts) (b) At what r-value(s) does f have a local maximum or minimum? (4 pts) (c) On what interval(s) is f concave upward or concave downward? (6 pts) (d) At what r-value(s) does f have an inflection point? (4 pts)