It is almost certain that Sandra left the apple. Chances are about even that Fred is in the office. It is improbable that Greg is a lion. Chances are slight that if either 'Greg is a lion' or 'Fred is in the office' but not both then Bernhard is a swan. It is likely that if 'Greg is a lion and Sandra left the apple' then Brian is white. It is likely that if either 'Fred is in the office' or 'Greg is a lion' but not both then Julius is a frog.
Chances are about even that 'Fred is in the office and Sandra left the apple'.
Chances are about even that 'Fred is in the office and Sandra left the apple'.
It is impossible that 'Fred is in the office and Sandra left 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
  0.95::factA.
  0.5::factB.
  0.1::factC.
  %hop1
  0.1::factX:-xor(factC,factB).
  0.7::factY:-and(factC,factA).
  0.7::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Fred is in the office and Sandra left the apple'.