Need help figuring this one out!

A cylindrical barrel is to be constructed to hold cubic feet of liquid. What are the dimensions of the barrel that minimize the amount of material used in it's construction?

I know that and

So i started out trying to find h : (Got this from calculating from the Volume definition)

Then I used the Area calculation :

Which turns out to :

This is where I become lost on what to do next. Any help would be appreciated!