Answer
$A: 0,0 \\ B: 2b,2c \\ C: 2a,0$
Work Step by Step
An ideally placed triangle, which we will call triangle ABC, should have point A placed at the origin and side AC be on the x-axis. Calling the length of AC "2a" and the coordinate of point B (2b,2c), we obtain:
$A: 0,0 \\ B: 2b,2c \\ C: 2a,0$
Note, there are now twos in front of the numbers, for the book asks for midpoints, meaning that we must double all of the values to get the length of the side as opposed to the lengths of half of a side.