Together with their two colleagues at GSIA Charles C. Holt and Franco Modigliani, Muth and Simon collaborated on "Planning Production, Inventories, and Work Force" (1960), a book on problems of production scheduling and inventory management for the firm. Their goal was to derive tractable, operational rules that could easily be applied in practice. Rather than a coincidence that the two apparently contradictory approaches to economic modeling were developed at GSIA at the same time, it is more likely that fruitful interaction in the quest to answer a common set of problems led the two researchers to two different solutions.