City of Ember

 In the city of Ember Lina and Doon get to pick their jobs. Lina chooses pipeworks laborer. Doon picked messenger. They each choose the thing they each didn't want but it happens that they had what each other wanted so they traded. Lina realizes that her job could be very dangerous if Ember's supply of light bulbs runs out she would have one of the most dangerous job in the city. Because Ember's only light is provided by street lights. Without the street lights it is pitch black