[yunwal]

The second thing is that even if students magically guessed that the line can grow after the government offers coffee, the answer is still wrong (or at least, makes unreasonable assumptions). The line will grow until the last person in line values coffee + berries as equivalent to the time to wait in line. This means everyone in front of that person still benefits from the coffee. How much social cost is created depends on the cost function of waiting in line, which is unstated.