Disclosed are a method and system for determining a retail price for a commodity within a geographic boundary. The roof has front, middle, and rear roof elements movable between a closed position covering a passenger compartment of the vehicle and an opened position stacked in a storage compartment of the vehicle. The distortion adjusting portion equalizes distortion generated in the direction of an inner diagonal line connecting the inner ends of the virtual quadrangle, with that generated in the direction of an outer diagonal line connecting the outer ends of the virtual quadrangle. This provides greater flexibility in network design and removes the need for middlebox information to be pre-configured at the middlebox control node. The device can be mounted vertically, horizontally, or otherwise for the convenience of the user. The resultant hearing aid will allow hearing impaired people to take advantage of cellular telephones and other recently-developed personal communication devices while also using their hearing aids.