although et some body to clarify this for you private messag is faster I'm not positive on the answer.
Because it must be 4 m from A and 2m from CD so first convert the cm into m. the 2.5 cm are 5m and the 4cm are 8m. Now 4m from A so starting from the corner A you go 4m. Now you are in between the line AB. You can then go up 2 or 3m because you will be spaced by 2m (5 - 2 = 3 so you still ahve enough space) so your answer would either be near the center or the corner B. Thats what I'm thinking anyways.
Hope this helps ;P