Show the manager name for all gas stations.
select manager_name from gas_station
Show those for gas stations belonging to the ExxonMobil company.
select t3.manager_name from station_company as t1 join company as t2 on t1.company_id = t2.company_id join gas_station as t3 on t1.station_id = t3.station_id where t2.company = 'ExxonMobil'