- Gener - 1. For the three options in the table, use the annual worth comparison and an interest rate of 10% per year to determine the option that is economically best. [7] IX X Y z First cost, $ -60,000 -200,000 -500,000 Annual O&M cost, $/year 12,000 Salvage value, $ 10,000 40,000 270,000 Life, years 3 10 50,000 40,000 * 2. Name the most important concept you have learned in the engineering economy. [1]