Six persons R, S, T, U, V, and W live in a building of six-floors such that the bottommost floor is numbered as 1 and the topmost floor is numbered as 6 but not necessarily in the same order. U lives just above R, who lives on a prime numbered floor. Two persons live between U and S. W lives just above S. T lives neither on a prime numbered floor nor above U. Who lives on second floor?