The present invention provides both a device and a method. The device comprises a plurality of light emitting elements arranged in line, and an optical system made of transparent material so as to allow the light outputted from the light emitting elements to enter and exit the optical system. A retrieval condition evaluating part evaluates each intermediate retrieval result obtained by the retrieval condition tree and determining a final retrieval result. The communication network then processes the updated location information for the mobile device to determine an updated rating the session, and applies the updated rating for prepaid charging for the session. When extended completely, the lap bar will remain locked in such position until the lap bar is rotated toward the position a person will occupy.