I can't say too much about Exam 2 because my hints may be jumping ahead of how you're thinking about the problem. This page mostly covers clarifications.
This is more a clarification in your understanding of the problem: What does n represent in this problem?
When I ask "What is the total waiting time of all customers?", I am looking for a formula, not an example with a total value.
You are given k air horns, but you don't know beforehand if k is enough airhorns to cover the given holes.