Recently, Johnson City replaced all paper-towel dispensers in lavatories of city buildings with electric hand dryers . The city estimates that in about fifteen years the amount that would otherwise have been spent on the purchase and disposal of paper towels will begin to exceed the cost of purchasing, installing, and operating the electric dryers. Therefore, despite high initial costs, replacing paper towels with electric hand dryers will be to the city’s long-term economic advantage.
Which of the following is an assumption on which the argument depends?