private static Move BackwardLeftForBlack(int r, int c, Board board){
        Move backwardLeft = null;
        
        assert(board.cell[r][c].equals(CellEntry.blackKing));
        if(r<Board.rows-1 && c<Board.cols-1 &&
           board.cell[r+1][c+1] == CellEntry.empty
          )
        {
            backwardLeft = new Move(r,c, r+1, c+1);
        }
        
        return backwardLeft;
    }