Monte Carlo Optimization: Anheuser$-$Busch loading problem

Anheuser$-$Busch $($AB$)$ delivers its beers to vendors using third$-$party delivery trucks. In order to save time and expedite the delivery, AB often preassembles beer crates into two trailer sizes which can be loaded at once into the third$-$party trucks. What we are trying to determine is the optimal size of these two trailers in terms of their weights. The goal is to minimize the total shipment cost which is calculated based on the following considerations:

The third$-$party trucks have weight $($Uniform$(10$k$,35$k$)$ lbs$.)$ and once loaded with the trailer their weight should not exceed $40$K lbs$.$

For each pound of weight that we go over $40$K lbs limit$,$ we must pay $$1$ per pound in overweight penalties.

For each unutilized pound of weight, we incur $$0\mathrm{.}75$ cost of idle capacity.