Multiple solutions possible? Help/explanation requested

[dancingartichoke]

I was doing this puzzle and got stuck at the end because it seemed to me that there are multiple possible solutions. I submitted this answer because by placing Ruben where I did, it forced June and Cynthia into their positions. It was marked correct, but why are the other ones wrong?

It seems that there are other solutions:

• June could be in the Sauna with Ruben in C3 OR
• June could be in the Workshop, Cynthia in the Nursery, and Ruben in C3, OR
• June in the Nursery, Cynthia in the Workshop, Ruben in C3, OR
• June in the Washroom, Cynthia in the Sauna, and Ruben in C3

Clearly it seems that this is the only solution where Ruben is in the fourth row. What forces him to be there?

clueprint-H4E8PBRC-solution.png

[admin]

If Ruben was in C3 it would invalidate clue #1. He would be the same number of steps from Briggs as Andrea.

[dancingartichoke]

Arghh! How did I not see that? Thank you!