Use the given graph of the function to answer the following questions. $[$Hint: All numerical values are whole numbers.$]$

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

Answer $($separate by commas, if necessary$)$:

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

Answer $($separate by commas, if necessary$)$:

$($c$)$ Find the coordinates of the relative minima of $.$ List your answers as points in the form $.$

Answer $($separate by commas, if necessary$)$:

$($d$)$ Find the coordinates of the points of inflection. List your answers as points in the form $.$

Answer $($separate by commas, if necessary$)$: