If you want to find the minimum side length of an easel that will support the whole sheet of paper, just divide the area by 2. Why? We know it's a square. So, the formula for finding the area of a square is A = s^2. Where is s is the side length of the square.
So, dividing by 2 will reverse it.
576 / 2 = 288
So, B. 288 inches is the answer.