Another question for you!

Farmer Ben has only ducks and cows. He can't remember how many of each he has, but he really doesn't need to remember. He does know that he has 22 animals, which is his age. He also remembers that those animals have a total of 56 legs, which is his father's age. Assuming that each animal is normal, how many of each does Farmer Ben have?

A diagram will help solve this one too!