Consider the equation below. (If an answer does not exist, enter DNE.) f( x) = x3 - 3x2 - 9x +6 (a) Find the interval on which f is increasing. (Enter your answer using interval notation.) Find the interval on which fis decreasing. (Enter your answer using interval notation.) (b) Find the local minimum and maximum values of f. local minimum value (3, - 21) X local maximum value (-1,11 ) X (c) Find the inflection point. (x, y ) = (1,5) X Find the interval on which fis concave up. (Enter your answer using interval notation.) Find the interval on which fis concave down. (Enter your answer using interval notation.)