A closed rectangle container with a square base must have a volume of 2250m^3. The material for the top and the sides of the container will cost $3/m^2. The material for teh bottom of the container will cost $2/m^2. Determine the dimensions of the box which will minimize the cost of the material for the box.

Now I know to find mins you take the 1st deriv test, but how do I apply this to this question?