Seven students A , B , C , D , E , F and G are living in a single room . They sleep on the following conditions .
I)A sleeps when D and F sleep .
II) E sleeps only when B sleeps .
III) E sleeps when C and G both sleep .
IV) C and G sleep when D sleeps .
V) D sleeps when F sleeps .
Which one should sleep first so that all the students could sleep .