The number of passengers who get on bus at loading station is Poisson random variable with mean 25. There are n>=1 stations after loading station. Each passenger is equally likely to get off at any one of remaining n stations, independently of where the other passengers disembark. The bus doesn't pick up any new passengers, and the bus only stops at those stations where some of its passengers need to get off. Calculate the expected number of stops that the bus will make till it has unloaded all of its passengers.