If you only use the desk and chair area "exclusively for business" (and the rest of the room for other purposes), you need to use the square footage that they take up. If that desk is also used for your personal use, then its not exclusive and doesn't qualify for the Office in Home.
♪♫•*¨*•.¸¸♥Lisa♥ ¸¸.•*¨*•♫♪
