Seven boxes B, C, D, P, Q, R and S are kept one over the other but not necessarily in the same order. Only three boxes are kept above B. Only one box is kept between P and B. Only three boxes are kept between P and R. R is kept at some place above B. D is kept immediately below R. Q is kept at one of the places above S. C is not kept immediately above or below P. Which box is kept at the lowermost position? 7941