13. (8 points) The graph of the derivative, f'(x), of a function f() is shown.
(a) (2 points) On what intervals is f(x) increasing or decreasing?
(b) (2 points) At what values of x does f(2) have local maximum or minimum?
(c) (2 points) In what interval is f(x) concave upward or downward?
(d) (2 points) What are the x-coordinates of the inflection points of f(x)?