We doubt that Greg is a rhino. It is probable that Julius is white. There is a better than even chance that Mary discarded the milk. It is almost certain that if 'Julius is white and Mary discarded the milk' then Sandra left the football. Chances are about even that if 'Julius is white and Mary discarded the milk' then Brian is white. There is a better than even chance that if either 'Mary discarded the milk' or 'Julius is white' but not both then John dropped the milk.
We believe that 'Sandra left the football and Greg is a rhino'.
There is little chance that 'Sandra left the football and Greg is a rhino'.
We believe that 'Sandra left the football and Greg is a rhino'.

  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
  0.2::factA.
  0.7::factB.
  0.6::factC.
  %hop1
  0.95::factX:-and(factB,factC).
  0.5::factY:-and(factB,factC).
  0.6::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Sandra left the football and Greg is a rhino'.