Question: A rectangular storage container is to have a volume of 10 meters cubed. The length of the base is twice the width. Material for the base costs $10 per square meter. Material for the sides and top costs $6 per square meter. Find the cost of the materials for the cheapest such container. ANS: $191.28

So I have and

Then rearranging V to get

What am I doing incorrectly? I subbed h into the A equation and solved dA/Dw equal to zero. . .

I got w = 1.5 and h = 20/9