The sisyphus monastery is on a hill, and every day donkeys climb the hill carrying water from the well in the valley. there are many donkeys, and they leave the well (at the bottom of the hill) every 15 minutes. they take one hour to climb the hill, 10 minutes to unload their water, and then half an hour to return to the well. when a donkey goes uphill carrying water, in the middle of the day, how many does it pass coming down?