Without doing the math, you can can see that the 100ft marker is about 1/3rd of the bottom(combining the triangle and the rectangle) This floor is practically(if not exactly) the same length of each vertical side of the building.
"100 x 3" is 300, So I am pretty sure the answer is 308.
Good luck!
-RxL
This is the same as 3/18 x 21/7, which you can simplify to 1/6 x 3, which is 3/6 also a half. So the answer is 1/2