A work cell at Chris Ellis Commercial Laundry has a workstation with two$$ machines, and each unit produced at the station needs to be processed by both of the machines.$($The same unit cannot be worked on by both machines$$ simultaneously.$)$ Each machine has a production capacity of $3$ units per hour.

Part $2$

The throughput time of the work cell

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enter your response here minutes per unit $($enter your response as a whole$$ number$).$