Why did the idea of using bus tokens to pay people from favelas for bringing in trash to a central location cost the city of Curitiba nothing?
(a) The buses belonged to the city of Curitiba
(b) The bus companies were paid based on how far the buses traveled
(c) The City saved money by not having to pick up the trash
(d) The City was able to recycle and sell much of the trash that was turned in