Anything helps please. I don't know where to start besides creating a formula.

Here is the problem.

A rectangular box with a square base and top is to have a volume of 20 ft^3. The material for the bottom costs 30cents per square foot, the material for the sides cost 10cents per squaring foot, and the material for the top costs 20cents per square foot. What is the minimum cost of contructing such a box?