It is highly unlikely that Mary grabbed the milk. It is unlikely that Greg is white. It is almost certain that Julius is a swan. Chances are slight that if either 'Mary grabbed the milk' or 'Greg is white' but not both then Fred put down the apple. It is likely that if 'Greg is white' or 'Mary grabbed the milk' or both then Bernhard is white. Chances are about even that if 'Greg is white' or 'Mary grabbed the milk' or both then Jeff left the apple.
It is almost certain that 'Mary grabbed the milk and Greg is white'.
There is almost no chance that 'Mary grabbed the milk and Greg is white'.
It is almost certain that 'Mary grabbed the milk and Greg 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
  0.05::factA.
  0.2::factB.
  0.95::factC.
  %hop1
  0.1::factX:-xor(factA,factB).
  0.7::factY:-or(factB,factA).
  0.5::factZ:-or(factB,factA).

  %hop2
  conclusion:-and(factA,factB).

  query(conclusion).
  
'Mary grabbed the milk and Greg is white'.