For each table in the database, identify the primary key and the foreign key$($s$).$ If a table does not have a foreign key, write None. Note that the database is composed of four tables that reflect these relationships:

An EMPLOYEE has only one JOB$\_$CODE, but a JOB$\_$CODE can be held by many EMPLOYEEs.

An EMPLOYEE can participate in many PLANs, and any PLAN can be assigned to many EMPLOYEEs.

Note also that the M:N relationship has been broken down into two $1$:M relationships for which the BENEFIT table serves as the composite or bridge entity.