Find the open interval$($s$)$ on which $f$ is concave upward.

Answer $($in help $($intervals$).)$

$2.$ Find the open interval$($s$)$ on which $f$ is concave downward.

Answer $($in help $($intervals$).)$

$3.$ Find the coordinates of the points of inflection. List your answers as points in the form $(x,y).$

Answer $($separate by commas if there is more than one point$)$