The manager controls and manages the fuel needs around the city and guides the workers of IOPL in the right way.
The maintainer is the person who maintains the tanks and the machines which are used by the workers in the IOPL. They too work for the fuel needs around the city.
The worker is the most important person in IOPL, who are the working souls of the city. They work for the fuel needs and too manages the storage of fuel in the IOPL.
The trainee is the newly joined worker who is taking starter guide/ training from the as the experienced worker in the IOPL.