Exercise 4.64: Louis Reasoner mistakenly deletes
the outranked-by rule (4.4.1) from the data base.  When he
realizes this, he quickly reinstalls it.  Unfortunately, he makes a slight
change in the rule, and types it in as


(rule (outranked-by ?staff-person ?boss)
  (or (supervisor ?staff-person ?boss)
      (and (outranked-by ?middle-manager
                         ?boss)
           (supervisor ?staff-person 
                       ?middle-manager))))

Just after Louis types this information into the system, DeWitt Aull comes by
to find out who outranks Ben Bitdiddle. He issues the query


(outranked-by (Bitdiddle Ben) ?who)

After answering, the system goes into an infinite loop.  Explain why.