Part D: In Savannah, Georgia, a single tour bus provides services to tourists. The bus departs as soon as there are 5 tourists present. Otherwise it waits until the arrival of the 5th customer before it begins the tour. The tour takes on average 1 hour. The total time follows an exponential distribution. The toursits arrive at a rate of 5 per hour based on a Poison process. Assume that there is waiting space for only 5 customers while the bus is on tour. Depict the rate diagram for this system and write down the balance equation for the state at which the bus begins its tour (i.e., arrival of the 5th customer). (10 points)