In many sports (for example professional baseball and basketball) the championship series lasts a maximum of seven games with the winning team being the first one to win four games. Assume the two teams are evenly matched, i.e. the probability of a given team winning is 1/2. What is the probability that the series will last

- four games?
- five games?
- six games?
- seven games?
- On average, how many games would one expect the series to last?