A rectangular box is to have a square base and a volume of 20 ft3. If the material for the base costs $0.30/square foot, the material for the sides costs $0.10/square foot, and the material for the top costs $0.20/square foot, determine the dimensions of the box that can be constructed at minimum cost.
The Attempt at a Solution
I know basic optimization... I will take the derivative to find a candidate for a relative minimum, and then verify it... But I REALLY need help trying to find the formula that I will use. I cannot seem to derive it from the information given. Any help is appreciated.