Consider a manufacturing process depicted by the following flowchart.

Station A has $3$ parallel operators, A$1,$ A$2,$ and A$3.$ Station C has $2$ parallel operators, $C1$ and $C2.$ Each unit only needs to be processed by one of the operators A$1,$ A$2$ and A$3.$ After being processed at Station B $($with a single operator$),$ a unit then needs to be processed by either $C1$ or $C2.$ The process time of the individual operators are given as follows.

$A1,A2,$ and $A3$:$18$ minutes

B: $11$ minutes

C$1$ and C$2$: $6$ minutes.