(25 points) A high-speed electronic assembly machine was purchased two years ago for $35,000. At the present time, it can be sold for $10,500 and replaced by a newer model having a purchase price of $21,250; or it can be kept in service for up to three more years. The new assembly machine, if purchased, has a useful life of not more than four years. The projected resale values and operating and maintenance costs for the challenger and the defender are shown in the accompanying table on a year-by-year basis. If the MARR is 15%, answer the following questions: Challenger Defender Operation & Operation & Market Market Year Maintenance Maintenance Value Value Costs Costs O $21,250 n/a $10,500 n/a 1 $7,000 $19,750 $3,000 $9,000 $8,000 $3.500 $9,000 $18,500 2 3 $17,500 $4,100 $10,000 $7.500 4 $16,750 $5,300 $7,000 $11,000 a. What is the Economic Life of the Challenger? (5 points) b. What is the Economic Life of the Defender? (5 points) c. Should the old model be replaced or not? If Yes, when and why? If No, why not? (15 points)