1. In the Central Railway station 15 computerised reservation counters are available. A customer can book his/her ticket in any train on any day in any one of these computerised reservation counters. The average time spent per customer by each clerk is 5 minutes. Average arrivals per hour during three types of activity periods have been calculated and customers have been surveyed to determine how long they are willing to wait during each type of period.

Type of period Arrivals per hour Customer’s acceptable waiting time Peak 110 15 minutes Normal 60 10 minutes Low 30 5 minutes Making suitable assumptions on this queuing process, how many counters should be kept open during each type of period.