An open topped rectangular box with a square base is to be constructed with a volume of $\displaystyle 32m^{3}$. Find the Dimension that require the lease amount of surface material.

and...

In microcomputers, most of the components are squeezed into a single box-shaped block. If the block has a length equal to twice the width and if the total surface area of the block must be $\displaystyle 200cm^{2}$ in order to dissipate the heat produced, find the dimensions for the maximum volume of the block.

I couldn't figure out how to get equations out of these two problems.

Thanks.