Question 8 (15 points) An engineer calculated the AW values shown for retaining a presently owned machine additional years. A challenger has an ESL of 7 years with AW = $$-86,000 per year. Assuming all future costs remain the same, when should the company replace the defender? The MARR is 12% per year. Assume used machines like the one presently owned will always be available. a) at year 2 AW of Years Defender, Retained Ob) at year 3 -92,000 -85,000 c) at year 4 -81,000 -89,000 d) at year 5 -95,000