Answer: The correct answer is "It would be more efficient for society to devote more resources to the production of beer.".
Explanation: If 4 million kegs of beer are sold,MC exceeds MB , which means that: It would be more efficient for society to devote more resources to the production of beer.
When producing 4 million barrels of beers, resources are not being used optimally, so more resources must be produced, so that resources can be used more efficiently (allocating less alternative resources).