The derivative of a function f is given by f'(x) = (x - 3)e^x for x > 0, and f(1) = 7.
(a) The function f has a critical point at x = 3. At this point, does f have a relative minimum, a relative
maximum, or neither? Justify your answer.
(b) On what intervals, if any, is the graph of f both decreasing and concave up? Explain your reasoning.
(c) Find the value of f(3).