Exercise 4.58.  Define a rule that says that a person is a ``big shot'' 
in a division if the person works in the division but does not have a 
supervisor who works in the division.

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(rule (big-shot ?person ?division)
  (and (job ?person (?division . ?x))
       (supervisor ?person ?super)
       (not (job ?super (?division . ?y)))))