It's just a simple matter of counting blocks.
To get from B to A you go right 4 blocks and down 2 blocks.
like the red lines below:



So to get from C to D you do the same thing. Go right 4 blocks 
and down 2 blocks.  And so you end up at (7,3):



Then you erase the red lines, and draw in the rest of the
parallelogram:



Answer: (7,3)

Edwin