(Figure: Understanding Surplus and Efficiency) In the graph, what is the efficient level of output? 
Definitions:
Opportunity Cost
The price of discounting the second most appealing alternative when engaging in decision-making.
Overtime Work
Overtime work refers to time spent working beyond the normal working hours, typically compensated at a higher pay rate.
Enjoyment
A feeling of pleasure and satisfaction obtained from various life activities or experiences.
Opportunity Cost
The financial implication of not selecting the following best possibility when faced with a decision.
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