An advertising manager has interviewed 2000 people to predict the effects of three advertising campaigns, with the following results: 580 people know campaign A, 840 people know campaign B, 920 people know campaign C, 260 people know campaigns A and B, 120 people know campaigns A and C but not campaign B, 300 know campaigns B and C, 100 people know all 3 campaigns. Determine the probability that a person knows at most 1 of these campaigns