Review the elevator queuing system in the TULT Building which has a peak traffic arrival rate of 15 students per class and an average of 9 classes on each floor. FTE classrooms are located on floors 10 to d. 14th floor, which is a total of 5 lecture floors. As many as 75% of students arrive within 15 minutes before class starts. The elevator service time is 1 second per floor plus 5 seconds of door opening and closing delay. It is known that there are 3 lifts, each of which can accommodate 8 people.

a. Calculate the amount of traffic offered on the queuing system!

b. What is the probability that a user will have to wait before being served?

c. If you want a waiting time of less than 3 minutes, specify the number of lifts needed!