21 points! What clues show on ** unconformity or gap in the horizontal rock layers? Which rock layers are missing? What might have happened to these rock layers? Please help me last question to my test and it's due in a hour!

Aproduction line at v. j. sugumaran's machine shop has three stations. the first station can process a unit in 7 minutes. the second station has two identical machines, each of which can process a unit in 16 minutes (each unit only needs to be processed on one of the two machines). the third station can process a unit in 10 minutes. ▼ is the bottleneck station, with a bottleneck time of nothing minutes per unit (enter your response as a whole number).