4. A twice differentiable function, f(x), has a domain of [-6, 6] (4) -6 < x < -2 x = -2 -2 < x < 0 x = 0 0 < x < 6 f' does not exist + does not exist a) Identify the value(s) of x over [-6, 6] for which f has a local minimum. b) Identify the interval(s) over [-6, 6] for which the function f is concave up. c) Identify the value(s) of x over [-6, 6] for which f has a point of inflection. d) Given f (-6) = 5, sketch a possible graph of f.