A container manufacturer is designing a retagular box, open at the top with a square base, that is to have a volume of 32 ft^3. If the box is to require the least amount of materials, what would be its dimensions?

I know that the answer to this equation is 4X4X2 but I'm not sure what equation to use to get this answer. I started by doing...

32= L*W*H

32= 2y*X

y=32-X/2

Am I on the right track or is there another equation I am suppost to use. If anyone know the answer could you please let me know. Thank you so much.