We doubt that Greg is yellow. It is highly unlikely that Lily is a rhino. We believe that Mary went to the hallway. Chances are about even that if 'Greg is yellow' or 'Lily is a rhino' or both then Brian is white. There is a better than even chance that if 'Mary went to the hallway and Lily is a rhino' then Jason is tired. There is little chance that if 'Greg is yellow and Lily is a rhino' then Bernhard is a frog.
It is impossible that 'Bernhard is a frog and Brian is white'.
It is impossible that 'Bernhard is a frog and Brian is white'.
It is highly likely that 'Bernhard is a frog and Brian is white'.

  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
  0.2::factA.
  0.05::factB.
  0.75::factC.
  %hop1
  0.5::factX:-or(factA,factB).
  0.6::factY:-and(factC,factB).
  0.1::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Bernhard is a frog and Brian is white'.