Just a few combinations would work...I'll try to create a solution...
1 step: Rectangle has 2 vertical and 2 horizontal lines.
You want to pick 2 vertical lines from the figure and two horizontal lines from the figure.
The side lengths are 2004 * 3(increased by 1), so we have 2004C2 * 3C2, the choose function means combinations.
Now, we have to get the non-shaded area, so is it 2*1002C2*3C2? Idk, can someone confirm
This is just complementary counting, so it is 1-X, the result. Is the answer \(\boxed{\frac{1002}{2003}}?\)
I'll try to confirm this later.