Three years ago a chemical processing plant installed a system at a cost of $20,000 to remove pollution from the waste waters that are discharged into a nearby river. This old system has no present salvage value and will cost $14,500 to operate next year, with operating costs expected to increase at rate of $500 per year thereafter. A new system has been designed to replace the existing system, and its installed cost of $9,000, with these costs increasing by $1,000 per year over its useful life of 12 years. Because the original system and the new system are specially designed for this particular chemical process, their salvage values at any future time are expected to be equal to zero. Should the company replace the existing pollution control system if the companys MARR is %12? Is it necessary to know the life of the defender?