Six people P, Q, R, S, T and U are living on a six different floors of the same building. The lowermost floor in the building is numbered 1, the floor above it, number 2 and so on till the topmost floor is numbered 6. R lives on the floor immediately below the floor of P. Q does not live on the topmost floor. T lives on the floor immediately below the floor of S. P does not live on any of the floors below S. Only three people live between the floors of U and T. T and U live on even numbered floors. Who lives on the floor number 4?