There is almost no chance that Daniel grabbed the milk. There is almost no chance that Jeff moved to the office. Chances are about even that Mary left the football. It is probably the case that if either 'Daniel grabbed the milk' or 'Mary left the football' but not both then Gertrude is a sheep. There is a very good chance that if either 'Jeff moved to the office' or 'Daniel grabbed the milk' but not both then Greg is yellow. It is almost certain that if 'Jeff moved to the office' or 'Mary left the football' or both then Brian is gray.
It is highly unlikely that 'Brian is gray' or 'Daniel grabbed the milk' or both.
Chances are about even that 'Brian is gray' or 'Daniel grabbed the milk' or both.
It is highly unlikely that 'Brian is gray' or 'Daniel grabbed the milk' or both.

  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
  0.02::factA.
  0.02::factB.
  0.5::factC.
  %hop1
  0.7::factX:-xor(factA,factC).
  0.8::factY:-xor(factB,factA).
  0.95::factZ:-or(factB,factC).

  %hop2
  conclusion:-or(factZ,factA).

  query(conclusion).
  
'Brian is gray' or 'Daniel grabbed the milk' or both.