you have asked to evaluate two pollution devices. the west scrubs cost 1000 to set up and 500 per year to operate. it must be completely replaced every 3 years, and it has no salvage value . dry scrub decice costs 2000 $ to set up and 300 per year to operate. it last for 5 years and has no salvage value . assuming pollution control equipment is replaced as ir wears out , whu h method do you recommend if wacc10 %