Answer:
D). $0
Step-by-step explanation:
Marginal cost is described as the 'increase in cost that accompanies a unit increase in the output.' It is characterized as the partial derivative of the cost function with respect to the output. It is calculated by the change in cost divided by the change in quantity. In the given case, the marginal cost for the second item would be $0 because it is for free and if we divide 0/1, we get 0. Thus, there is no additional cost for producing that extra good and hence, option D is the correct answer.