Maxima and minima section

I was assigned a homework problem in my max and min section, and one problem has me completely stooped. It doesn't even provide me a function to work with, and I looked above and below the problem with no clue. The problem is:

Find the shape of the rectangular box of volume Vzero for which the sum of the edge lengths is least.

Keep in mind that for all the other problems assigned I was using the Second Partials Test, which consisted of D = D(xo,yo) = fxx(xo,yo)*fyy(xo,yo) - f^2xy(xo,yo). Thanks in advance.