Suppose you stood on line as part of a group of 30 people waiting to receive a vaccine. After everyone finished, you were told that ten members of the group turned out to have cases of Covid. You never came down with the infection, so you couldn’t have been one of the ten. If you were neither first nor last in line, what is the probability that at least one of the two people next to you in line had the virus (but you got lucky and didn’t catch it anyway) ?