I) Six students P, Q, R, S, T and U are in a class.
II) Q and R are lighter than U but taller than P.
III) S is taller than Q and heavier than R.
IV) T is lighter than S but heavier than U.
V) U is taller than S.
VI) P is lighter than T but heavier than U
VII) P is taller than T.
Who among the students is the shortest?