It is improbable that Bernhard is a frog. Chances are slight that Brian is white. Chances are slight that Mary got the football. We doubt that if 'Mary got the football and Brian is white' then Winona is a wolf. There is almost no chance that if 'Brian is white and Bernhard is a frog' then John discarded the apple. It is unlikely that if either 'Bernhard is a frog' or 'Mary got the football' but not both then Greg is a lion.
It is impossible that 'John discarded the apple and Winona is a wolf'.
It is impossible that 'John discarded the apple and Winona is a wolf'.
We believe that 'John discarded the apple and Winona is a wolf'.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  0.1::factA.
  0.1::factB.
  0.1::factC.
  %hop1
  0.2::factX:-and(factC,factB).
  0.02::factY:-and(factB,factA).
  0.2::factZ:-xor(factA,factC).

  %hop2
  conclusion:-and(factY,factX).

  query(conclusion).
  
'John discarded the apple and Winona is a wolf'.