farmer brown had three pens each same number animals pen held cows pen b held sheep

Farmer Brown had three pens, each with the same number of animals. Pen A held cows, Pen B held sheep, and Pen C held pigs. One day, his careless nephew released all the animals from their pens. The farmer rushed to get the animals in any pen. Each pen now held a mixed group of cows, sheep, and pigs. He noticed the following: Each pen held the same number of animals as it did before the animals were released. The number of pigs in pen A was the same number of pigs in pen B. The number of sheep in pen A was the same number of sheep in pen C. The number of sheep in pen A was 2/3 the number of pigs in pen A. How does the number of cows in pen B compare with the number of cows in pen C?