For f' (x) = (x -5)'(x - 4) (x + 1)', which of the following statements is true? O a) f has a local maximum at x = -1 and a local maximum at x = 4 O b) f has a local minimum at x = -1 and no local extrema at x = 5 O c) f has no local extrema at x = - 1 and a local maximum at x = 4 o d) f has a local maximum at x = -1 and no local extrema at x = 4