How hard is it to expand a set-covering model to accommodate new cities? Answer this by modifying the model in Figure 14.55. Add several cities that must be served: Memphis, Dallas, Tucson, Philadelphia, Cleveland, and Buffalo. You can look up the distances from these cities to each other and to the other cities in a reference book (or on the Web), or you can make up approximate distances.
a. Modify the model appropriately, assuming that these new cities must be covered and are candidates for hub locations.
b. Modify the model appropriately, assuming that these new cities must be covered but are not candidates for hub locations.