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Constrained Minimization Problem(HELP )

1. Homework Statement
A closed rectangular box is made with two kinds of materials. The top and bottom are made with heavy-duty cardboard costing $0.36 per square foot, and the sides are made with lightweight cardboard costing $0.06 per square foot. Given that the box is to have a capacity of 162 cubic feet, what should its dimensions be if the cost is to be minimized?


2. Homework Equations
Surface Area A=2xy+2xz+2yz
Volume= V=xyz=162

partial derivitations are required to do this(which i know how to do)


3. The Attempt at a Solution
The hard part that I am trying to figure out is creating the Cost equation. All I need to know is what that equation would be and I can take care of everything afterwards. Like mentioned before in (2), the surface area A=2xy+2xz+2yz, but I have no idea how im going to create a cost function including the prices mentioned in the problem. PLEASE HELP. BLESS ANYONE WHO DOES. THANK YOU SO MUCH IN ADVANCE!!!
 

tiny-tim

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… The top and bottom are made with heavy-duty cardboard costing $0.36 per square foot, and the sides are made with lightweight cardboard costing $0.06 per square foot.

I have no idea how im going to create a cost function including the prices mentioned in the problem.
Hi MathNoob123! :wink:

Multiply the area of heavy-duty cardboard by the cost per area, and multiply the area of lightweigh cardboard by the cost per area, and add :smile:
 
Hi MathNoob123! :wink:

Multiply the area of heavy-duty cardboard by the cost per area, and multiply the area of lightweigh cardboard by the cost per area, and add :smile:

I have already solved the problem, but thank you very much for replying. Really appreciate it.
 

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