Answer:
(b). outweighs the extra cost
Explanation:
As per the principles of marginal analysis, the extra benefit of performing a task must outdo the extra cost associated with the same.
Marginal refers to something extra which is earned or incurred when an additional unit of output is produced/sold.
So as per marginal principle, an activity should only be taken up if extra benefit derived from it exceeds the extra cost that would be incurred.
Hence, the correct option is (b). outweighs the extra cost.
