A rectangular sheet of metal measures 6cm by 8cm. Four equal squares are cut from each corner of the sheet (so it looks like a net of a rectangular prism, without the lid) and the remaining metal is bent to form an open ended rectangular tray. (so the equation of the volume would be V=4x(4-x)(3-x)]

I) What would be the largest possible value of x?

II) What would be the smallest possible value of x?

Is there a way to do this without calculus?