3. A window frame manufacturer is searching for ways to improve revenue from its triple insulated sliding windows. The costs and savings related with each alternative are shown below. a) Use the present worth method to select the more economical alternative at a MARR of 6% per year. b) Are these alternatives mutually exclusive or independent? Why? Initial cost, $ A 600,000 increasing by $80,000 per yr B 400,000 20,000 the first year increasing 20% per yr Annual revenue, $/yr 100,000 the first year thereafter thereafter Annual costs, $/yr 20,000 10,000 Upgrade cost at year 2, $ 10,000 26,000 Salvage Value, $ 12,000 17,000 Life, years 4 6