Answer:
There will be 5 customers on average at the coffee urn at any time.
Explanation:
The waiting line model explains that the average number of customers im the system at any time, L, is related to the average rate of arrivals of customers, λ and the average service rate, μ through the relation
L = λ ÷ (μ - λ)
L = ?
λ = 2.5 customers per minute
Each customer spends an average of 20 seconds in the shop.
Time spent in the shop = 20 seconds per customer = (20/60) minutes per customer = 0.333333 minutes per customer.
μ = (1/0.3333) = 3 customers are in the shop per minute.
L = λ ÷ (μ - λ)
L = 2.5 ÷ (3 - 2.5)
L = 5 customers.
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