(1 point) Let f(x) = -x4 - 6x3 + 5x - 6. Find the open intervals on which f is concave up (down). Then determine the x-coordinates of all inflection points of f. f is concave up on the intervals 2. f is concave down on the intervals 3. The inflection points occur at x = Notes: In the first two, your answer should either be a single interval, such as (0,1), a comma separated list of intervals, such as (-inf, 2), (3,4), or the word "none". In the last one, your answer should be a comma separated list of x values or the word "none". Note: You can earn partial credit on this