<image>There is a service area between City A and City B. A passenger bus departs from City A to City B and a truck departs from City B to City A at the same time, traveling at a constant speed. The function relationships of the distances of the passenger bus and the truck from the service area, denoted as \( y_{1}(km) \) and \( y_{2}(km) \) respectively, with the travel time \( x(h) \), are shown by solid lines in the graph. 

(1) The distance between City A and City B is ____ \( km \);

(2) Derive the function relationship between the distance \( y_{2}(km) \) of the truck from the service area and the travel time \( x(h) \) after 3 hours of departure;

(3) At the same time as the passenger bus and the truck depart, a postal vehicle leaves from the service area to City A to pick up goods and then returns to City B (the time to pick up goods is negligible). The function relationship between the distance \( y_{3}(km) \) of the postal vehicle from the service area and the travel time \( x(h) \) is shown by the dashed line in the graph. Directly state how long it takes during the journey for the postal vehicle to have the same distance from the service area as the passenger bus and the truck.