It is certain that Greg is a frog. Chances are slight that Sandra dropped the milk. It is likely that Brian is green. It is certain that if 'Greg is a frog and Sandra dropped the milk' then Daniel took the football. It is unlikely that if 'Sandra dropped the milk and Brian is green' then Bernhard is gray. It is probable that if 'Brian is green' or 'Sandra dropped the milk' or both then Sumit is thirsty.
It is almost certain that 'Sumit is thirsty and Brian is green'.
Chances are about even that 'Sumit is thirsty and Brian is green'.
It is almost certain that 'Sumit is thirsty and Brian is green'.

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

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

  query(conclusion).
  
'Sumit is thirsty and Brian is green'.