notice the picture
the semicircle, has a radius of "r", you can use that to get the area of a circle, then half it, that's the area of that semicircle in "r" terms,
now, look at the rectangle the semicircle is sitting on top of, to make up
the normal window, it has a height of 3r, and notice its width
so, get the area of the semicircle, and the area of the rectangle,
both in r-terms
add them up, and that's the area of the window
