If the smaller square has a perimeter of 8, then each side has a length of 2. The large square, with a perimeter of 20, thus has 5 as the length of each side. By looking at the figure, you can see that each of the rectangles contains 2 sides of the length of the smaller square, and 2 sides equal to the length of the larger square. The sum of the perimeters of the 2 shaded rectangles would therefore be 2(2+2+5+5)=28, or E.