A flexible optical disk, includes a disk substrate, wherein a rigidity of the disk is equal to or more than 5 Pa and equal to or less than 5000 Pa where the rigidity is defined as Young’s modulus of the disk\xd73. Plans containing recommendations are then presented to a system user so the user can make decisions necessary regarding whether to change configuration hardware to meet expected load increases in the future. As the mass is accelerated by the mass-moving actuator, the entire vibrotactile unit vibrates. The number of sheets in each booklet is determined and is stored. Concept vectors are assembled for the identified concepts based on articles in the corpus and social media usage. Each pad has an inclined upper end surface with a given inclination angle such that the upstream end of the inclined upper end surface is higher in level than the downstream end thereof.