Response B is better because it explains the math clearly and stays honest about the missing quantity column. Response A reaches the same answer, but it sounds more certain than the image supports. B feels accurate, careful, and useful.

Response B does a better job because it breaks down the math in a way that's easy to follow and admits when information is missing from the quantity column. Response A gets to the same answer but comes across as too confident given what we can actually see in the image. Response B strikes the right balance by being precise, cautious, and helpful at the same time.