It is highly likely that Mary went to the office. It is likely that Julius is yellow. There is a very good chance that Gertrude is a cat. Chances are about even that if either 'Julius is yellow' or 'Gertrude is a cat' but not both then Greg is white. It is probably not the case that if 'Julius is yellow and Mary went to the office' then Lily is a lion. There is little chance that if either 'Julius is yellow' or 'Mary went to the office' but not both then John dropped the apple.
It is impossible that 'Lily is a lion and John dropped the apple'.
It is impossible that 'Lily is a lion and John dropped the apple'.
It is almost certain that 'Lily is a lion and John dropped 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
  0.9::factA.
  0.7::factB.
  0.8::factC.
  %hop1
  0.5::factX:-xor(factB,factC).
  0.25::factY:-and(factB,factA).
  0.1::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Lily is a lion and John dropped the apple'.