Dimensions of box that minimize the material used

[Winzer]

Homework Statement

A box with a square base and open top must have a volume of 32,000cm^3. Find the dimensions of the box that minimize the amont of material used.

Homework Equations

$$Sa(surface area)=4xy+x^2$$
$$Volume=x^2y$$

The Attempt at a Solution

I want to minimize Sa I am pretty sure so how do i begin?

 

[Winzer]

Never mind I figured it out.