Spread of rumors. In a town of n 1 inhabitants, a person tells a rumor to a second person, who in turn repeats it to a third person, etc. At each step the recIpIent of the rumor IS chosen at random from the n people available. Find the probability that the rumor will be told r times without: (a) returning to the originator, (b) being repeated to any person. Do the same problem when at each step the rumor is told by one person to a gathering of N randomly chosen people. (The first question is the special case N