If calls arrive at a telephone exchange such that the time of arrival of any call is independent of the time of arrival of earlier of future calls, the probability distribution function of the total number of calls in a fixed time interval will be

An unbiased coin is tossed an infinite number of times. The probability that the fourth head appears at the tenth toss is

Two independent random variables $$X$$ and $$Y$$ are uniformly distributed in the interval $$\left[ { - 1,1} \right].$$ The probability that max $$\left[ {X,Y} \right]$$ is less than $$1/2$$ is

A fair dice is tossed two times. The probability that the $$2$$^nd toss results in a value that is higher than the first toss is