Answer
$A: 0,0 \\ B: b,c \\ C: a+b, c \\ D: a,0$
Work Step by Step
An ideally placed parallelogram, which we will call parallelogram ABCD, should have point A placed at the origin and side AD be on the x-axis. Calling the length of AD "a" and the coordinate of point B (b,c), we obtain:
$A: 0,0 \\ B: b,c \\ C: a+b, c \\ D: a,0$
