In one or two sentences, explain why people will do less of an activity when the marginal costs are greater than the marginal benefits.

Marginal cost is defined as the additional cost incurred in adding a unit of product or service.

Marginal benefit is defined as the additional satisfaction or utility that the individual receives from consuming the added unit of product or service. 

In every endeavor, we weigh the benefit and cost of a certain product, course of action or service. We aim to get the most out of every product or decision. We are driven to reach maximum profit at a minimum cost.

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