Absolute maximum at $s$, absolute minimum at $r$, local maximum at $c$, local minima at $b$ and $r$, neither max nor min at $a$ and $d$.
Work Step by Step
$s$ and $r$ are the extrema of the function because they are the highest and lowest value of the function, respectively. $c$ is a local maximum because it is the highest point in its neighborhood, and since $b $ and $r$ are the lowest in theirs, they are local minima. $a$ and $d$ fit none of these descriptions, so they are neither max nor min.