Discuss the characteristics of the problem presented by the design of the U.S. Merchant Marine Fleet. What are the basic elements of the problem? What assumptions are being made in order to develop a mathematical model? Do these assumptions reduce the realism and, therefore, the usefulness of the model significantly? What is the primary role of the model? How do you envision that the model will be used in supporting decisions regarding the planning of the fleet? What important considerations are omitted from the model formulation?