A first apparatus for processing a liquid sample is disclosed. The reference structure has at least one reference element that is registrable in a computer assisted navigation system. The operation may include performing an inventory check on the at least one additional listing. The first rail and the second rail each include an orientating rail and a guiding rail. As a result, the air-fuel ratio correction coefficients is not be thrown into confusion and no phenomenon of the air-fuel ratio being thrown into confusion occurs even if the control parameter is changed in accordance with operating conditions of the engine.