Acost of choosing to attend a concert is not only the out-of-pocket $ $ $ cost, but also the "opportunity cost" (lost wages or maybe extra sleep). every activity we undertake requires us to not pursue other opportunities.

The correct answer is real cost.

Explanation:

The real cost of attending a concert includes both explicit as well as an implicit cost. The explicit cost is the direct cost paid out of pocket. For instance, the cost of concert tickets, transport cost, cost incurred on food and beverages, etc are the direct or explicit cost.  

The implicit costs are the indirect costs which are not directly incurred. The main example of implicit cost is the opportunity cost of attending the concert. Opportunity cost is the cost involved in sacrificing the alternative. For instance, if a person is taking leave from work then the wages that he/she could have earned is an opportunity cost.

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