For the next problem, explain and justify your answers. (3 pts.) The derivative function f (x ) is shown below (continued on the next page): 4- 3- f ' (x) (a) On what interval is the function f (X) increasing? Explain why. (b) At what value(s) of x does f (x) has a local maximum? Why? (c) On what interval(s) is f (x) concave downward? Why