Etermine the intervals on which the following function is concave up or concave down. identify any inflection points. f left parenthesis x right parenthesisf(x)equals=negative 5 x superscript 4 baseline plus 20 x cubed minus 5−5x4+20x3−5 determine the intervals on which the following functions are concave up or concave down. select the correct choice below and fill in the answer box(es) to complete your choice. (simplify your answer. type your answer in interval notation. use a comma to separate answers as needed.) a. the function is concave downdown on nothing and concave upup on nothing. b. the function is concave down on nothing. c. the function is concave up on nothing.