You have the following additional information about the pieces: The Queen is an all-attacking piece, i.e. it can attack any other piece (King or Rook) from its position. On the other hand, no King can attack any other chess-piece. Rooks are friendly and won't attack each other.
Toby Gottfried created this applet to help solve the puzzle: http://www.gottfriedville.net/puzzles/grid/chess.htm
Source: Sudipta Das.