Chances are slight that Lily is green. We doubt that Mary is in the school. It is probably the case that Brian is a frog. We doubt that if 'Brian is a frog' or 'Lily is green' or both then Julius is white. It is highly unlikely that if either 'Brian is a frog' or 'Mary is in the school' but not both then Greg is a swan. We doubt that if 'Lily is green and Mary is in the school' then Jeff left the apple.
Chances are about even that 'Mary is in the school and Julius is white'.
There is almost no chance that 'Mary is in the school and Julius is white'.
Chances are about even that 'Mary is in the school and Julius 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
  0.1::factA.
  0.2::factB.
  0.7::factC.
  %hop1
  0.2::factX:-or(factC,factA).
  0.05::factY:-xor(factC,factB).
  0.2::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Mary is in the school and Julius is white'.