Originally Posted by

**MarkFL2** Yes, there will be the base, whose area you have already found is $\displaystyle A_b=2w^2$ and the 4 sides. Now, you should have the area of the sides is:

$\displaystyle A_s=\frac{30}{w}$

Both of these are in square meters. So, now you want to construct the cost function. Take the cost of the material per square meter times the area in square meters to get the cost, then sum these together to get the total cost in dollars:

$\displaystyle C(w)=10A_b+6A_s$

Now, minimize this function.