A simple manufacturing process has five steps. Step $1$ can process a unit in $7$ minutes. Step $2$ can process a unit in $6$ minutes. Step $3$ uses two identical machines, each of which can process a unit in $8$ minutes $($each unit only needs to be processed on one of the two machines$).$ Station $4$ can process a unit in $3$ minutes. Step $5$ can process a unit in $5$ minutes. Which step is the bottleneck?

Step $4$

Step $1$

Step $3$

Step $5$

Step $2$