Aerotron Electronics is considering purchasing a water filtration system to assist in circuit board manufacturing. The system costs $40,000. It has an expected life of 7 years, at which time its salvage value will be $7,500. Operating and maintenance expenses are estimated to be $2,000 per year. If the filtration system is not purchased, Aerotron Electronics will have to pay Bay City $12,000 per year for water purification. If the system is purchased, no water purification from Bay City will be needed. Aerotron Electronics must borrow half of the purchase price, but they cannot start repaying the loan for 2 years. The bank has agreed to three equal annual payments, with the first payment due at the end of year 2. The loan interest rate is 8 percent compounded annually. Aerotron Electronics' MARR is 10 percent compounded annually.
a. What is this investment's external rate of return?
b. What is the decision rule for judging the attractiveness of investments based on external rate of return?
c. Should Aerotron Electronics buy the water filtration system?