Reconsider Prob. 9.2-21 involving a contractor (Susan Meyer) who needs to arrange for hauling gravel from two pits to three building sites.
Susan now needs to hire the trucks (and their drivers) to do the hauling. Each truck can only be used to haul gravel from a single pit to a single site. In addition to the hauling and gravel costs specified in Prob. 9.2-21, there now is a fixed cost of $50 associated with hiring each truck. A truck can haul 5 tons, but it is not required to go full. For each combination of pit and site, there are now two decisions to be made: the number of trucks to be used and the amount of gravel to be hauled.
(a) Formulate an MIP model for this problem.
(b) Use the computer to solve this model.