Two assumptions to be clarified in the interview: 4th question above doesn't apply to the top boss (who can't have a greater salary than a boss he/she doesn't h

Two assumptions to be clarified in the interview: 4th question above doesn't apply to the top boss (who can't have a greater salary than a boss he/she doesn't have, so no issue on the 1st question). Department table has an alternate key on department name.