Answer
We can rank the points according to the magnitude of the net angular momentum:
$a \gt b = c \gt e \gt d$
Work Step by Step
Let $d$ be the length of each side of the square.
We can find the angular momentum relative to each point:
point a:
$L = 0+mvd+mvd = 2~mvd$
point b:
$L = 0+0+mvd = mvd$
point c:
$L = 0+0-mvd = -mvd$
point d:
$L = 0+mvd-mvd = 0$
point e:
$L = \frac{mvd}{2}+\frac{mvd}{2}-\frac{mvd}{2} = \frac{mvd}{2}$
We can rank the points according to the magnitude of the net angular momentum:
$a \gt b = c \gt e \gt d$
