Two 8" holes is close. Area is the difference of the square of a side (square) or diameter (circle), so a 4" circle has four times the surface area of a 2" circle. pi x radius squared gives the area of a circle.
The area of a 6" circle = 3.14 x 3 squared = 3.14 x 9 = 28.25 square inches
28.25...