A process depicted in the picture. After being processed in the first station, a box needs to be processed at either Machine A or Machine B for the parallel line. The box isprocessed at Stations $3$ and $4$ before leaving the production line. The process time of each station$/$machine is indicated in the flowchart $($e$.$g$.,5$ min$/$A work cell in a local manufacturer has a workstation with $4$ machines that form a line $($Machine $1-$Machine $2-$Machine $3-$Machine $4).$ Each unit needs to pass through each machine in order to be completed. Each machine has a production capacity of four units per hour. What is the process time of the work cell in minutes per unit?

Question $15$ options:

$15$

$16$

$8$

$4$box means that the process time is $5$ minutes to process each box at the machine$/$station$).$ What is the process time of this system measured in$$min$/?$