What are strategies for handling multiple students visiting office hours? Context: I am an assistant professor of mathematics at a small liberal arts college in the US.

I hold a scheduled office hour every weekday, plus additional hours near exams.  Office hours are a significant part of my institution's culture, and they are regularly used by our students.  As such, it is not uncommon for multiple students with entirely different questions to visit at the same time.

I am somewhat unsure about how I should handle this.  If they all have the same question, I can easily work with a small group simultaneously on the white board in my office.  Otherwise, I can only think of the following options:


Work with students on a first-come, first-serve basis.  Move to the second student once finished with the first, then to the third after the second, etc.
Work with students on a first-come, first-serve basis, but only give each student 10-15 minutes before I move to the next one.
Rotate between students, answering a few minutes worth of questions before going to the next student, and eventually circling back.
Tell students that if they want to meet for more than 15 minutes they must make an appointment outside office hours.


Our department has several tables in the hallway, so I usually go with option 3.  That said, this method seems inefficient for the students and can be exhausting for me, so I am wondering if I can do any better.  Most of my own undergraduate professors used option 1, but I really disliked how a single student could consume nearly all of their time.
I would suggest an alternative: rotate after each question, not after each student. So solve a question from one student, then allow a different student to ask a different question. If multiple classes are present, you can go by class rather than by student.

This has several advantages:


Everyone will prioritize their questions: no one feels rushed by the people behind them, nor like they wasted a trip because of someone in front of them
Students (in the same class) may not all have the same questions, but they'll benefit from seeing how you approach each problem.
Students in different classes can digest your previous answers and try to apply those concepts to new questions while they wait for you to circle back
This should be helpful for the majority of students -- if there are any special cases (e.g., students with individual issues that aren't useful to the rest of the group), they'll see what's going on and will appreciate your invitation to schedule an appointment
You get to keep your position at the whiteboard, which is less exhausting for you