It is probably not the case that John discarded the milk. Chances are about even that Fred is in the office. It is unlikely that Brian is a frog. There is almost no chance that if 'Fred is in the office' or 'Brian is a frog' or both then Sumit is hungry. We believe that if 'John discarded the milk and Brian is a frog' then Winona is a mouse. We believe that if 'John discarded the milk and Fred is in the office' then Bernhard is white.
It is highly unlikely that 'Fred is in the office' or 'Sumit is hungry' or both.
Chances are about even that 'Fred is in the office' or 'Sumit is hungry' or both.
It is highly unlikely that 'Fred is in the office' or 'Sumit is hungry' 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
  0.25::factA.
  0.5::factB.
  0.2::factC.
  %hop1
  0.02::factX:-or(factB,factC).
  0.75::factY:-and(factA,factC).
  0.75::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Fred is in the office' or 'Sumit is hungry' or both.