A square has all of sides equals. So in the bottom of box you have a square 2x2 and the formula for volumen is width*length*thicknes, from the data 2*2*t=200 cubic inches, solve for t=50 inches. Now for an open box you have 4 pieces around the square in the bottom, you add 50+2+50=102 inches, for lenght and width 102inches