The shaded region outside the small square but inside the large rectangle models the grass in Shannon’s back yard. A rectangle has a width of 7 x minus 5 and height of 4 x. A smaller box is inside of the rectangle with side lengths of x.

If the dimensions given are measures in feet, which expression represents the area of the shaded region?
27 x squared minus 20 x
18 x squared minus 15 x
20 x minus 27 x squared
15 x minus 18 x squared