Answer
Absolute maximum at $r$, absolute minimum at $a$, local maxima at $b$ and $r$, local minimum at $d$, neither a maximum nor a minimum at $c$ and $s$.
Work Step by Step
$r$ and $a$ are the absolute extrema of the function because they are the highest and lowest value of the function, respectively. $b$ and $r$ are local maxima due to the fact they are the greatest value in their neighborhoods, and similarly $d$ is a local minima since it is the smallest value in it's neighborhood. $c$ and $s$ do not fall into any of these descriptions, so they are neither.
