There is a better than even chance that John got the milk. It is highly likely that Greg is a lion. Chances are about even that Sandra grabbed the apple. We believe that if 'Sandra grabbed the apple' or 'Greg is a lion' or both then Bernhard is white. It is unlikely that if either 'Greg is a lion' or 'John got the milk' but not both then Mary dropped the milk. There is a very good chance that if 'Greg is a lion and John got the milk' then Brian is gray.
There is a very good chance that 'Mary dropped the milk and Bernhard is white'.
It is highly unlikely that 'Mary dropped the milk and Bernhard is white'.
There is a very good chance that 'Mary dropped the milk and Bernhard 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
  0.6::factA.
  0.9::factB.
  0.5::factC.
  %hop1
  0.75::factX:-or(factC,factB).
  0.2::factY:-xor(factB,factA).
  0.8::factZ:-and(factB,factA).

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

  query(conclusion).
  
'Mary dropped the milk and Bernhard is white'.