b) (10%) When should the old PCB machine be replaced? Justify your answer.c) (5%) If the useful life of the defender and challenger were given differently or the studyperiod was different the useful life of the alternatives, do you still follow the same solutionprocedure? Explain your answer in detail and if there is any assumption you need to make,please state it as well.

3. (35%) A PCB machine was purchased two years ago for $100,000. At the present time, it can be sold for $50,000 and replaced by a newer model having a purchase price of $85,000; or it can be kept in service for a maximum of two more year. The new PCB machine, if purchased, has a useful life of not more than two years. The projected resale values and operating and maintenance costs for the challenger and the defender are shown below table on a year-byyear basis. The MARR is 15%. l m 62,000 $20,000 34,000 $27,000 some 25,000 - seooo a) (20%) Calculate the economic life of challenger and defender. Show all your calculations