Just think about it
right angles are the very definition of perpendicular
how many right angles in a full rotation? 4
answer is 4
I actually did this problem today for edge , I included a picture that I used to understand how to do this problem the answer is 1%.
As a practical equation, this one doesn't make much sense -- why would the profit per person have a term proportional to the number of people? Let's just go with it.



That's the answer to the first part.
35/x represents a portion of the profit that's 35/x per person, or a constant $35 per tour.
5500 is the awnser I came up with