In Exercises 39 through 42, the derivative f'(x) of a differentiable function f (x) is given. In each case,

(a) Find intervals of increase and decrease for f(x).

(b) Determine values of x for which relative maxima and minima occur on the graph of f(x).

(c) Find f"(x), and determine intervals of concavity for the graph of f(x).

(d) For what values of x do inflection points occur on the graph of f(x)?

f'(x) = x²(x + 1)³