using a computer, generating required service characteristic information that indicates user requirements for a service related to subject product offer, the user requirements being obtained from user preference data related to the service;

using the computer, storing the required service characteristic information in a storage device;

using the computer, prompting to input user evaluation data regarding each piece of the generated required service characteristic information and user satisfaction level data regarding each piece of the required service characteristic information;

using the computer, outputting a list of the input evaluation data and the input satisfaction level data on a display device in a visually recognizable manner as required service characteristic evaluation information for each piece of the required service characteristic information;

using the computer, prompting selection of the required service characteristic evaluation information, and setting a target satisfaction level regarding the selected required service characteristic evaluation information, based on the satisfaction level data and the evaluation data output on the display device; and

using the computer, outputting calculated importance level of each function necessary for implementing the required service characteristic, on the display device based on an input of a correlation value between the required service characteristic information and information of the function necessary for implementing the required service characteristic.