Fifty percent of the square footage of a corridor may be excluded from the definition of floor area if a window with a clear, non-tinted, glazed area of at least 20 square feet is provided in such corridor, provided that such window:

(a)        shall be directly visible from at least 50 percent of the corridor or from the vertical circulation core.  This standard shall be achieved when a visually unobstructed straight line can be drawn between such corridor, elevator or stairwell, and the window; and

(b)        is facing a street, yard or court that meets the applicable regulations set forth in Article II, Chapter 3.