F
The formula for area is length times height. If you add 1/2 to 2.5 for each of the boxes, you will be adding a total of 1 to the smallest in order to get the area of the largest. If you add 1 to 2.5, you get 3.5. Multiply 3.5 times 3.5, you get 12.25. That is how you get the answer.
