$3\mathrm{.}97$ An explosion in an LNG storage tank in the process of being repaired could have occurred as the result d static electricity, malfunctioning electrical equipment. an open flame in contact with the liner, or purposful action $($industrial sabotage$).$ Interviews with eng. neers who were analyzing the risks involved led to es$.$ timates that such a explosion would occur with prot ability $0\mathrm{.}25$ as a result of static electricity, $0\mathrm{.}20$ as a result of malfunctioning electric equipment, $0\mathrm{.}4022$ result of an open flame, and $0\mathrm{.}75$ as a result of purposful action. These interviews also yielded subjective of timates of the prior probabilities of these four causo of $0\mathrm{.}30,0\mathrm{.}40,0\mathrm{.}15,$ and $0\mathrm{.}15,$ respectively. What wo the most likely cause of the explosion?