How much time should be allocated to supervising undergraduate researchers? I recently asked this question about how many office hours per week are common for undergraduate lecturers but then I just read this one about supervising research done by undergrads. This got me thinking that perhaps my previous question was going in the wrong direction.

I have >300 students in 3 different subjects. 200 of those students are in one subject and that subject requires students to do extensive research. My challenge (explained in the question linked above) is that I seem to have too little time to properly support this many students.

These are business students so there is no lab. The research is reading the literature, finding data, integrating the two into some meaningful insight.

So, my question is, when supervising undergraduate students who are doing research, how much time on average, per week, per student, should this consume of the supervisor's time? 15 minutes? 30 minutes? 1 hour?

Edit: To put this in perspective, the students are not writing a bachelor thesis. However, they are expected to put in about 100 hours of non-class time (after the class time has finished) doing their research and writing it up. The final product is about 4,000 - 5,00 words (so far less than a thesis).
One person cannot possibly supervise 200 undergraduate research projects per semester of any substance. This sounds more like a term paper with a research component than 200 fully-fledged research projects. When I did undergraduate research, it was a 20-hour per week job that I got paid for, and even then my supervisor and I rarely met for more than half an hour per week. 

There are only 168 hours total in one week, and only 40 working hours in a week. If you spent your entire job meeting with all of the students every week, you could give them 12 minutes each. This is clearly impossible. 200 students is so many that giving them each a 30-minute kickoff meeting to discuss their initial idea at the beginning of the semester would take you two and a half weeks. This would put some students at a serious disadvantage over others by potentially delaying their project start or leaving them confused about what is required of them.

If these are not much more than a term paper, then one person can probably do this by putting the assignment together on paper or in email and only answering questions during normal office hours. These kinds of assignments have clearly articulated goals and guidelines and apply techniques as laid out in lectures and homeworks. If you want a more substantial, independent project, then you need TA support, at least 6 and as many as 20 TAs to cover 200 students.