If one of the site visits includes both Quinn and Sasada, which one of the following could be true?

I am having confusion on this question because Vandercar cannot be the only site visited. If that was true that would mean that he is visiting Farmington, which means he is in the 2nd site. That would mean that S and R are going on the third visit. This goes completely against the 4th rule which says S has to be before V... Can someple please explain this to me