.
                                     We
                          e         bW           e
                       b            e b              b
                      W           We               W
                      e               b                   e
                     b               W                   b
                     W            e     b              W
                      e             W   e               e
                       b            b   W             b
                        W           e  b            W
                           e           W            e
                               b       e         b
                                         b