   solve(L).
   solve([boat(set([taylor, umugu])),
          boat(set([taylor])),
          boat(set([nzwawe, amoc])),
          boat(set([umugu])),
          boat(set([taylor,helen])),
          boat(set([taylor,nzwawe])),
          boat(set([taylor,william])),
          boat(set([amoc])),
          boat(set([umugu,nzwawe])),
          boat(set([umugu])),
          boat(set([umugu,amoc]))
          ]).
