Answer:
The correct answer is: the opportunity cost of producing the last hamburger equals the marginal benefit of consumption.
Explanation:
The equilibrium quantity of hamburgers is 50 million.
The equilibrium price of each unit of hamburgers is $5.
The economy is producing at 50 million output and $5 price.
This implies that the economy is in equilibrium. At equilibrium, the cost of producing will be equal to benefit. Thus we can say that the economy is producing at efficient level.
In case the cost is higher than the marginal benefit, it implies that production is inefficient.