The circumference of a rectangle = the circumference of a circle+the length of two radii = 3. 14× radius× 2+2× radius = radius× (3.14× 2+2) = radius× (6.28+2) = 24.84.

Therefore, the radius = 24.84 ÷ (6.28+2) = 3 decimeters.

Therefore, the area of the circle = 3. 14× 3× 3 = 28.26 square decimeter.