There are six boxes, namely P, Q, R, S, T, U, which are kept one above the other. R is kept immediately above P. T is kept immediately above U. Only two boxes are kept between T and S. T is not at the topmost or at the lowermost position. P is above U. Q is kept immediately above S. R is neither kept immediately above nor immediately below T. U is kept at one of the positions above S. There are only 2 boxes between R and U. Which of the following boxes is kept immediately below U?