Consider the following graph. y un -3 X 1 2 3 4 5 6 (a) Find the interval(s) on which f is increasing. (Enter your answer using interval notation.) (b) Find the interval(s) on which f is decreasing. (Enter your answer using interval notation.) (c) Find the open interval(s) on which fis concave upward. (Enter your answer using interval notation.) (d) Find the interval(s) on which fis concave downward. (Enter your answer using interval notation.)