Apply M/M/1 Model for capacity planning.
A company has a central document-copying service. Arrivals are assumed to follow the Poisson distribution, with a mean rate of 15 per hour (λ=15). Service times follows the exponential distribution, with average service time of 2 minutes (µ=30 copies / hr).
A) What is the mean number of customers in service?
B) How many chairs should be provided for those waiting in line if we aim to the goal that people will find a chair to wait 90% of the time? Calculate cumulative probability till it reaches 90%.