__ and __ live on same floor. 

There are two floors between the floors of U and Y (both of them may or may not live in the same type of flat). U lives south west of B. U lives on first floor.   X lives 2 floors above B (both live in the same type of flat).   D lives immediately above Z, who doesn’t live below anywhere B’s floor. So, Y must live above U’s floor either in flat A or B. Both X and B live in flat B. Case 1: When Y lives in the flat B. A lives above D’s floor but not in flat A. W doesn’t live in a prime numbered floor. C doesn’t live immediately above B. So, A lives in on 5th floor in flat B. Case 2(b): When both Y and U live in the same flat and U live on 1st floor The final arrangement is as follows: