Customers in a small retail store arrive at the cashier at the rate of $10$ per hour. The average service time for the cashier is five minutes. Arrivals tend to follow a Poisson distribution, and service times follow an exponential distribution.

SINGLE$-$SERVER MODEL

Average utilization of the system

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Probability that n customers are in the system

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Probability that zero customers in the service system

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Average number of customers in the service system

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Average number of customers in the waiting line

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Average time spent in the system, including service

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Average waiting time in line

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What is the average number of customers in the system?