Consider the function. (if an answer does not exist, enter dne.) f(x) = x4 − 6x3 (a) determine intervals where f is increasing or decreasing. (enter your answers using interval notation.) increasing decreasing(b) determine the local minima and maxima of f. (enter your answers as comma-separated lists.) locations of local minima x = locations of local maxima x = (c) determine intervals where f is concave up or concave down. (enter your answers using interval notation.) concave up concave down (d) determine the locations of inflection points of f. (enter your answers as a comma-separated list.) x =