In an enclosure, there are 10 cows and 5 bulls on a farm. Due to overcrowding in the current enclosure, 6 animals will be moved to another enclosure. In how many ways can the owner do this if he wants to move 3 cows and three 3 bulls:
if it doesn't matter which cow and which bull is moving,
if the oldest bull must be in the new enclosure,
if the 2 oldest bulls are not allowed in the new enclosure,
if he wants to keep the 3 youngest cows in the current enclosure?