Which one of the following families could live in the house that is the farthest east?

In the scenario that has M as 3, slots 5,6, & 7 can possibly have R,N,O,P, and L. And for the scenario where M is 5, slots 6 & 7 are P & L respectively. So since P is the constant one in both scenarios that would go on the east side on both scenarios that is why I chose it. N could go on slot 7 making that the furthest east but not for scenario where M is 3. Please explain and if possible by diagramming M as 3 & M as 5 to see what I missed. Thank you!