It is highly unlikely that Brian is white. It is improbable that Julius is a frog. It is probably not the case that John went to the office. It is highly likely that if 'John went to the office' or 'Brian is white' or both then Winona is a wolf. There is little chance that if 'Julius is a frog and Brian is white' then Mary dropped the apple. Chances are about even that if 'Brian is white and Julius is a frog' then Greg is a rhino.
There is a very good chance that 'Brian is white and Mary dropped the apple'.
It is impossible that 'Brian is white and Mary dropped the apple'.
There is a very good chance that 'Brian is white and Mary 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
  0.05::factA.
  0.1::factB.
  0.25::factC.
  %hop1
  0.9::factX:-or(factC,factA).
  0.1::factY:-and(factB,factA).
  0.5::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Brian is white and Mary dropped the apple'.