operations research questions

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Eat & Gas convenience store operates a two-pump gas station. The lane leading to the pumps can house at most 3 cars, excluding those being serviced. Arriving cars go elsewhere if the lane is full. The distribution of arriving cars is Poisson with mean 20 per hour. The time to fill up and pay for the purchase is exponential with mean 6 minutes. What is the Probability that an arriving car will start service immediately without waiting in the lane. Answer: Drake Airport services rural, suburban, and transit passengers. The arrival distribution for each of the three groups is Poisson with mean rate of 15, 10, and 20 passengers per hour, respictively. The time to check in a passenger is exponential with mean 6 minutes. if the number of counters provided at Drake is 5, the total average time to check a customer is 15 minutes, Po = 0.00496, Lq = 6.86. What is the Expected Waiting Minutes in Queue