(8). The graph of f'(x) of the continuous function f (x) is given below: f(x) 10- 5 -10 -5 10 -10- Using the graph above, please answer the following questions: (a) On what intervals is the graph of f(x) concave up? (b) On what intervals is the graph of f (x) concave down? (c) At what values of x does the graph of f(x) have inflection points