1'} Assume that we have four cities to, any and 2. The four cities are locates on the corners of a square. There is an electric line which we designate by a going from at to a. Another line designated by E: goes from a to 9-. Finally there is a line going from y to z denoted by c, whilst line :1 gm from 2 to to. There is a line I from n to 3. There are no other lines connecting the cities. Hence, the ling build a square with diagonals inside. Let A be the event that line it works... whilst B is the event that line I: works. Finally let C be the event that line c works... let D be the event that line d works let F he the event that 1' works ..... All these lines work independently of each other. We assume that the probabilities P53=Piii Pbi=P(B)J pc=P(U]1- Pd:=-P(D}:PI=P{F]" are all known. a} Calculate the probability that electricity can ow from a: to z, (in terms of pa, p1,, pm pd, pf}. b} Given that electricity can ow from s to 2, what is the probability {conditional probability] that :1 works