Final answer:
The marginal utility per dollar for the second box of paper clips is zero.
Step-by-step explanation:
The marginal utility per dollar represents the additional utility gained from spending an additional dollar on a specific item. In this case, the question is asking about the second box of paper clips. Since we don't have any specific information about the price or utility of the second box, we can't determine the exact marginal utility per dollar. Therefore, the answer is d. Zero.