Answer:
Future costs which will be different under the two alternatives.
Step-by-step explanation:
In simple words, while considering to replace the new machinery every entity must focus comely on two main aspects which are the historical cost or the cost at which the old machine could be sold and the future costs which will significantly affects the potential profits of the subject firm.
However, due to various different methods of depreciation and future value estimations one should consider all the methods in hand and then take the decision.