You can use Interest tables

6. A company is considering replacing its air conditioner. Management has narrowed the choices to two alternatives that offer comparable performance and considerable savings over their present system. The effective annual interest rate is 8%. What is the net annual benefit of each system? Which one would you recommend? Initial Cost Estimated Life Salvage Value Annual Savings System $7000 15 years $500 $1500 System II $9000 15 years *- $1250 $1900 At the end of life, you have to pay someone $1250 to haul it away