It is probable that Sumit is thirsty. It is unlikely that Gertrude is a sheep. There is almost no chance that Sandra dropped the milk. It is almost certain that if either 'Sandra dropped the milk' or 'Sumit is thirsty' but not both then Julius is white. It is likely that if 'Sandra dropped the milk' or 'Sumit is thirsty' or both then Brian is white. We doubt that if 'Sandra dropped the milk and Gertrude is a sheep' then Mary got the football.
It is unlikely that 'Mary got the football' or 'Gertrude is a sheep' or both.
It is unlikely that 'Mary got the football' or 'Gertrude is a sheep' or both.
It is certain that 'Mary got the football' or 'Gertrude is a sheep' 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
  0.7::factA.
  0.2::factB.
  0.02::factC.
  %hop1
  0.95::factX:-xor(factC,factA).
  0.7::factY:-or(factC,factA).
  0.2::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Mary got the football' or 'Gertrude is a sheep' or both.