Read the following statements and answer the questions: There are six flats on a floor in two rows facing north and south allotted to six persons, P, Q, R, S, T and U. The positions of their flats are as follows :
I. Q's flat faces the north and is not next to S.
II. S and U have occupied diagonally opposite flats.
III. R, next to U, occupies a flat facing the south and T gets a flat which faces the north.
Whose flat is between Q and S?