You have been asked to evaluate 2 pollution control devices. The wet scrub costs $100 to set up and $50 per year to operate. It must be completely replaced every 3 years, and it has no salvage value. The dry scrub device costs $200 to set up and $30 per year to operate. It lasts for 5 years and has no salvage value. Assuming that pollution control equipment is replaced as it wears out, which method do you recommend if the cost of capital is 10 percent?