The perimeter of the window is 30 ft.

 be the width of the rectangle.

So the diameter of the semicircle is also .

Then radius of the semicircle is .

Consider  be the length of the rectangle.

The perimeter of the rectangle is .

Circumference of the semicircle is .

Substitute  in the above circumference.

Perimeter of the window = perimeter of the semicircle + perimeter of the rectangle.

.

Area of the semicircle is .

Substitute  in the above area.

Area of the rectangle is 

Substitute  in the area of the rectangle.

Area of the window = area of the semicircle + area of the rectangle

The area of the window is .

The area of the window is .