Computing an absolute difference includes receiving a first value and a second value. For example, in some embodiments, the user is permitted to perform various functions, such as, browsing the service, navigating external links, and viewing various pages of other users and groups. The apparatus has a trouble recognition mechanism for recognizing trouble in the battery and a resetting mechanism for resetting the battery in accordance with the recognition by the trouble recognition mechanism. The outside surfaces of the minor hulls are parallel to the vessel’s centerline, whereas the outside surfaces of the major hull aftwardly slant toward the centerline. A coupling member is provided that secures a portion of the cable in a generally coiled configuration, and the coupling member is constructed to be decouplable to release a portion of the length of the cable in the generally coiled configuration in response to a force that is less than the linear breaking strength of the cable.