In each of a packet of cigarettes there is one of a set of cards numbered from 1 to n. If a number N of packets is bought at random, the population of packets is large and the numbers are equally...

In each of a packet of cigarettes there is one of a set of cards numbered from 1 to n. If a number N of packets is bought at random, the population of packets is large and the numbers are equally frequent, show that the probability of getting a complete set of cards is