A man starts at the point o on the map below. he chooses a path at random and follows it to point b1, b2, or b3. from that point, he chooses a new path at random and follows it to one of the points a1

A man starts at the point o on the map below. he chooses a path at random and follows it to point b1, b2, or b3. from that point, he chooses a new path at random and follows it to one of the points a1 – a7. suppose the man arrives at point a4, but it is not known which route he took, what is the probability that he passed through each of the four points: b1, b2, b3? calculate each one.