It is probably the case that Fred dropped the apple. There is a better than even chance that Emily is a mouse. Chances are slight that Julius is a frog. It is highly unlikely that if either 'Emily is a mouse' or 'Fred dropped the apple' but not both then Jeff went to the bedroom. It is likely that if either 'Emily is a mouse' or 'Fred dropped the apple' but not both then Daniel took the milk. It is unlikely that if 'Julius is a frog' or 'Fred dropped the apple' or both then Bernhard is white.
It is certain that 'Bernhard is white' or 'Daniel took the milk' or both.
Chances are about even that 'Bernhard is white' or 'Daniel took the milk' or both.
It is certain that 'Bernhard is white' or 'Daniel took the milk' or both.

  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
  0.7::factA.
  0.6::factB.
  0.1::factC.
  %hop1
  0.05::factX:-xor(factB,factA).
  0.7::factY:-xor(factB,factA).
  0.2::factZ:-or(factC,factA).

  %hop2
  conclusion:-or(factZ,factY).

  query(conclusion).
  
'Bernhard is white' or 'Daniel took the milk' or both.