There is little chance that John picked up the apple. It is probably not the case that Bernhard is green. Chances are slight that Greg is yellow. It is highly unlikely that if 'John picked up the apple and Greg is yellow' then Mary dropped the milk. We doubt that if either 'John picked up the apple' or 'Bernhard is green' but not both then Lily is a rhino. It is unlikely that if 'Bernhard is green and Greg is yellow' then Julius is a lion.
It is almost certain that 'Greg is yellow and John picked up the apple'.
There is almost no chance that 'Greg is yellow and John picked up the apple'.
It is almost certain that 'Greg is yellow and John picked up the apple'.

  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
  0.1::factA.
  0.25::factB.
  0.1::factC.
  %hop1
  0.05::factX:-and(factA,factC).
  0.2::factY:-xor(factA,factB).
  0.2::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Greg is yellow and John picked up the apple'.