Chances are about even that Sandra dropped the milk. It is highly unlikely that Bernhard is green. There is little chance that Fred is in the school. We doubt that if either 'Fred is in the school' or 'Sandra dropped the milk' but not both then Lily is white. It is impossible that if either 'Sandra dropped the milk' or 'Fred is in the school' but not both then John went to the garden. There is a very good chance that if 'Sandra dropped the milk' or 'Bernhard is green' or both then Greg is yellow.
It is probable that 'Greg is yellow and Bernhard is green'.
It is highly unlikely that 'Greg is yellow and Bernhard is green'.
It is probable that 'Greg is yellow and Bernhard is green'.

  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
  0.5::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.2::factX:-xor(factC,factA).
  0.0::factY:-xor(factA,factC).
  0.8::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Greg is yellow and Bernhard is green'.