Q. Students arrive randomly at help desk of computer lab. There is only one service agent, also time requisite d for inquiry varies from student to student. Arrival rates have been found to follow Poisson distribution; also service times follow negative exponential distribution. Average arrival rate is 12 students per hour; also average service rate is 20 students per hour. Elucidate how many students, on average, will be waiting in line at any one time?