And d) At what x-value does f have an inflection point? Please write clear and neat!!

Let f(x) = 915/3 - 18x2/3. Use exact values for each. (a) On what interval(s) is f increasing or decreasing? (b) At what r-value(s) does f have a local maximum or minimum? (c) On what interval(s) is f concave upward or concave downward