Answer:
The old computer should be replaced since the differential amount of the replacing it with a new computer is $10,000
Explanation:
                                          Old machine      New machine       Differential 
                                                                                                    amount
purchase cost                  $0                      ($15,000)               ($15,000)
operating costs year 1     ($24,600)          ($19,600)                $5,000
operating costs year 2    ($24,600)          ($19,600)                $5,000
operating costs year 3    ($24,600)          ($19,600)                $5,000
operating costs year 4    ($24,600)          ($19,600)                $5,000
<u>operating costs year 5    ($24,600)          ($19,600)                $5,000   </u>
TOTAL                              ($123,000)         ($113,000)              $10,000