It is probable that Bernhard is a swan. It is probably not the case that Lily is a swan. It is probably not the case that Mary moved to the office. Chances are about even that if 'Lily is a swan and Mary moved to the office' then Greg is yellow. We doubt that if 'Bernhard is a swan' or 'Lily is a swan' or both then Brian is a frog. There is little chance that if 'Mary moved to the office and Bernhard is a swan' then Sandra dropped the apple.
It is probably the case that 'Sandra dropped the apple and Mary moved to the office'.
There is almost no chance that 'Sandra dropped the apple and Mary moved to the office'.
It is probably the case that 'Sandra dropped the apple and Mary moved to the office'.

  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.
  0.25::factB.
  0.25::factC.
  %hop1
  0.5::factX:-and(factB,factC).
  0.2::factY:-or(factA,factB).
  0.1::factZ:-and(factC,factA).

  %hop2
  conclusion:-and(factZ,factC).

  query(conclusion).
  
'Sandra dropped the apple and Mary moved to the office'.