An empty bottle moves up and down as the water waves pass beneath it. however, it doesn't move toward the shore with the waves. What does this demonstrate about the propagation of wave through a medium?

Consider a production line with five stations. station 1 can produce a unit in 9 minutes. station 2 can produce a unit in 10 minutes. station 3 has two identical machines, each of which can process a unit in 12 minutes (each unit only needs to be processed on one of the two machines. station 4 can produce a unit in 5 minutes. station 5 can produce a unit in 8 minutes. which station is the bottleneck station?