The correct answer is C. incremental cost.
An incremental cost is the additional cost incurred when a company makes a decision. It is the difference between the costs of two alternatives. In this case, the incremental cost is the additional cost incurred to bring the processed product to the next production stage.
A partial cost is a cost that is incurred for a specific activity, but is not the only cost associated with that activity. For example, the cost of raw materials is a partial cost of manufacturing a product.
A relevant cost is a cost that is relevant to a decision. It is a cost that will change if the decision is made. In this case, the incremental cost is a relevant cost because it will change if the company decides to bring the processed product to the next production stage.
An irrelevant cost is a cost that is not relevant to a decision. It is a cost that will not change if the decision is made. In this case, the cost of the equipment used to manufacture the product is an irrelevant cost because it will not change if the company decides to bring the processed product to the next production stage.