We doubt that John moved to the office. There is a better than even chance that Greg is a frog. There is a very good chance that Brian is gray. There is little chance that if 'Brian is gray' or 'John moved to the office' or both then Mary went to the office. There is a better than even chance that if 'Greg is a frog and Brian is gray' then Jeff left the apple. Chances are slight that if 'John moved to the office' or 'Brian is gray' or both then Gertrude is a mouse.
There is a very good chance that 'Jeff left the apple' or 'Brian is gray' or both.
There is a very good chance that 'Jeff left the apple' or 'Brian is gray' or both.
Chances are slight that 'Jeff left the apple' or 'Brian is gray' 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
  0.2::factA.
  0.6::factB.
  0.8::factC.
  %hop1
  0.1::factX:-or(factC,factA).
  0.6::factY:-and(factB,factC).
  0.1::factZ:-or(factA,factC).

  %hop2
  conclusion:-or(factY,factC).

  query(conclusion).
  
'Jeff left the apple' or 'Brian is gray' or both.