Dean Foods Dairy switched from delivery trucks with regular gasoline engines to ones with diesel engines. The diesel trucks cost $2,000 more than the ordinary gasoline trucks but $600 per year less to operate. Assume that Dean Foods saves the operating costs at the end of each month. If Dean Foods uses a discount rate of 1 percent per month, approximately how many months, at a minimum, must the diesel trucks remain in service for the switch to be sensible?

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