There are 4 identical dice which are similar in all respects, such that you cannot make out one from the other. All 4 identical dice are rolled together. In how manydifferent ways are the outcomes possible?

P and Q are two points 100 km apart. A starts running from P towards Q at 10 km/hr. B starts running from Q at exactly the same time and in the same direction asthat of A at 20 km/hr. After an hour, B turns back and changes his speed to 10 km/hr. After another hour, B again turns back and changes his speed to 20 km/hr. Hekeeps on changing his speed and direction in this manner till the time he meets A. After how much time will A and B meet for the first time?