NOTE: When using interval notation in WeBWorK, remember that:
You use 'INF' for $\infty$ and '-INF' for $-\infty$.
And use 'U' for the union symbol.
Enter DNE if an answer does not exist.

a) Determine the intervals on which $f$ is concave up and concave down.
$f$ is concave up on:
$f$ is concave down on:

b) Based on your answer to part (a), determine the inflection points of $f$. Each point should be entered as an ordered pair (that is, in the form $(x, y)$).
c) Find the critical numbers of $f$ and use the Second Derivative Test, when possible, to determine the relative extrema. List only the $x$-coordinates.