A method for extending the warranty on a first good by purchasing additional, related goods, involves a determination of the cost per unit time of the warranty extension for the first good based on information received about such first good. The raw measured value of the measuring sensor is corrected by a multiplicative correction value and an additive correction value, which are both taken from a characteristic map. Therefore, use of the MFP and specific functions of the MFP can be restricted according to the particular registered user.