You work for a logistics company and your manager has asked you to evaluate their shipping and outbound system queue. Specifically, the manager wants to better understand the relationship between packing rates and the resulting average amount of time a package spends in the system. The warehouse's average service rate is a function of the number of servers working such that (number_of_workers*72 = average_packages_serviced_per_hour) . At any given time, the manager can have 16 to 24 workers in the warehouse. Assuming the warehouse operation meets M/M/1 model assumptions and has an average package arrival rate of 1000 packages/hour, what is the minimum number of workers required to meet the threshold of 12 seconds for the average time a package spends in the system?