Two one-way subway lines, the A train line and B train line, intersect at the transfer station. A and B trains arrive at station according to independently operating. Rate of Train A is 3 Trains/hr, rate of Train B is 6 Trains/hr. We suppose that passenger boarding and unboarding haapens almost instantaneously, not unlike true rush-hour conditions in several cities throughout world. i) Find probability that station handles exactly nine trains during any given hour? ii) If observer counts number of trains that station handles every hour, starting at 8:00 A.M. on Tuesday, find expected number of hours until he or she will first count exactly nine trains during an hour which commences on hour?