The number 540 is also composite, which is required in your answer.
The other numbers do not end in 0,2,4,6 or 8, which is required to be divided evenly by 2. And only answer choices A. B. and C. can be evenly divided by 3.
This question is asking for the area of the carpet. For a triangle you would do the same equation as a square (length x width) divided by 2. This is 4.8 x 5.2 = 24.96/2 = 12.48