3. A cover must be added to the box and it is made having the same costs as the box bottom.
Determine the new total cost, the new box dimensions, and the number of ferry trips required
to transport the 400 cubic yards of gravel.
 R.J. Dufﬁn, E.L. Peterson and C. Zener, Geometric Programming, John Wiley and Sons, New
York, 1967. 21