When a teacher in a private school points out to her high school principal that since there are empty seats in all classrooms, the cost of additional students is really zero, she is using the

The answer is "Principal of marginal analysis".

Step-by-step explanation:

To determine unless the benefits of even an aggressive resource would outweigh its costs, and therefore increase utility, individuals and businesses can use a valuation model to compare the risks versus the benefits of more activities, like whether to create or consuming more. It's the amount during which net value is greater than or equal to marginal cost that's the optimal quantity in this situation. The amount where the marginal social cost curve and consumer surplus line connect.

4th option is correct xy=-10

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