Exercise 4.57: Define a rule that says that
person 1 can replace person 2 if either person 1 does the same job as person 2
or someone who does person 1’s job can also do person 2’s job, and if person 1
and person 2 are not the same person. Using your rule, give queries that find
the following:


 all people who can replace Cy D. Fect;

 all people who can replace someone who is being paid more than they are,
together with the two salaries.