11-3. The Universal Postal Service is considering the possibility of fixing wind deflectors on the tops of 500 of their long-haul tractors. Three types of deflectors, with the following characteristics, are being considered (MARR = 10% per year): Windshear Blowby Air-vantage Capital investment $1,000 $400 $1,200 Drag reduction 20% 10% 25% Maintenance per $10 $5 $5 year Useful life 10 years 10 years 5 years If 5% in drag reduction means 2% in fuel savings per mile, how many miles do the tractors have to be driven per year before the windshear deflector is favored over the other deflectors? Over what range of miles driven per year is air-vantage the best choice? (Note: Fuel cost is expected to be $4.00 per gallon, and average fuel consumption is 5 miles per gallon without the deflectors.) State any assumptions you make. (11.2)