Which of the following Flat is vacant?

Answer the questions based on the information given below. Eleven persons A, B, C, D, P, Q, R, S, X, Y and Z live in four storey building having four floors such that lowermost floor is numbered as 1 and floor immediately above the lowermost floor is numbered as 2 and so on. Each floor has 3 flats numbered as 1, 2 and 3 from west to east such that flat – 1 is in west of flat – 2 and flat – 2 is in west of flat – 3. One of the flats on a floor is vacant. The dimensions of each of the flats are same. Note: If there is one/two floor(s) between two flats then they may or may not have the same flat number of different floors. Z lives in an even numbered flat on floor number 2. B and C live on same floor. B lives in an even numbered flat on lowermost floor. R and A live on same floor. All the flats on the floor on which Q lives are occupied. X lives to the west of R. B lives on the floor on which two other persons live. There is one floor between R and Q. P’s flat is immediately above C’s flat and the numbers of their flats is same. R lives immediately below the vacant flat and the flat number of vacant flat and R is same. D lives somewhere above Y in same flat number, but not on flat 3.A lives in flat – 1.