1. A transportation problem involves distributing stocks or merchandise from multiple sending points (origins) to multiple receiving points (destinations).

2. The transportation model is a linear programming model that minimizes the expense of shipping goods from several origins to several destinations. There will be an equality constraint for each supplier and for each destination.

3. Total supply must equal total demand in order to solve the problem.

1. If total supply is less than total demand, add a supply constraint to make them equal, with zero shipping costs.
2. If total supply is greater than total demand, add a demand constraint to make them equal, with zero shipping costs.

4. Solve the problem with linear programming software.