(d) X -6 -4 -2 2 4 6 -2- -4 -6 (i) Identify the critical numbers of f. (Enter your answers as a comma-separated list.) X = (ii) Identify the open interval(s) on which f is increasing or decreasing. (Enter your answer using interval notation.) increasing decreasing (i) Determine whether f has a relative maximum, a relative minimum, or neither at each critical number. (Enter your answers as a comma-separated list.) relative minimum X = relative maximum X