Answer:
Retain Replace Net income
Increase/Decrease
Variable manufacturing costs 4241300 3205300 1036000
New machine cost 0 378500 -378500
Sell old machine 0 -34700 34700
Total 4241300 3549100 692,200
Conclusion: The old factory machine should be replaced as its net income is lesser
Workings
Variable manufacturing costs
a. Retain Equipment = 605900*7 = 4241300
b. Replace Equipment =457900*7 = 3205300