.
                                      Bill
                    ­             C   Bill     C
                              o      Bill        o
            ­                 s        Bill          s
                            b        C  ­ o          b
                            y       s       b        y
                            B       y      B        B
                              i       i       l         i
                               l        l   C        l
                                 l        o        l
                                           s    
                                           b
                                           y