John D. C. Little is an Institute Professor and the Chair Management Science at the MIT Sloan School of Management. He formed the Little's law in 1961. It states: "The average number of customers in a system (over some interval) is equal to their average arrival rate, multiplied by their average time in the system." A corollary has been added: "The average time in the system is equal to the average time in queue plus the average time it takes to receive service." Prof. Wikipedia
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