You are given an operations process with $9$ stages. Stage one has a process time of $1$ week, stage two is $2$ weeks, stage three is $3$ weeks, stage four is $4$ weeks, stage five is $5$ weeks, stage six is $6$ weeks, stage seven is $21$ weeks, stage eight is $7$ weeks, and stage nine is $21$ weeks. Stage nine is last.

So stage $7$ and $9$ are bottlenecks with $21$ weeks$/$unit$.$ Correct me if I am wrong but currently we have a yearly capacity of $52/21=2\mathrm{.}48$ units.

I want to increase the capacity, let's say I can draw a total of $3$ parallel lines to the system. What is the best new assembly line?