Letang industrial systems company (lisc) is trying to decide between two different conveyor belt systems. system a costs $280,000, has a four-year life, and requires $85,000 in pretax annual operating costs. system b costs $360,000, has a six-year life, and requires $79,000 in pretax annual operating costs. both systems are to be depreciated straight-line to zero over their lives and will have zero salvage value. whichever project is chosen, it will not be replaced when it wears out. the tax rate is 23 percent and the discount rate is 10 percent.