Two roads join Ashville and Benson, and two further roads join Benson to Carlyle. Ashville is directly connected to Carlyle using a railroad. All four roads and the railroad are independently blocked by mudslides with probability p.
(a) If you are at Ashville, what is the probability you can travel to Carlyle, and
(b) if you get there, what is the probability that the railroad is blocked?