1. A method comprising: calculating a plurality of areas where a mobile body may arrive on a basis of dynamic map information; calculating, for an event occurring in the plurality of areas, an arriving probability of arriving at a region affected by the event; extracting an avoidance position for enabling the mobile body to avoid arriving at the region affected by the event; calculating an encountering probability of meeting the region affected by the event on a basis of a reliability of the event, an arriving probability, and an avoidance position; and notifying the mobile body of the encountering probability.