A web server is connected to the router as shown below to provide the service. The availability information of the wire and recently purchased web server is provided as $0\mathrm{.}99$ and $0\mathrm{.}95,$ respectively, while the availability of the router is unknown. However, it has been observed that on average the failure occurs approximately $20$ weeks after the previous failure and four repairing times are reported as $42\mathrm{.}7,40,41\mathrm{.}5,$ and $42$ hours. Determine the overall availability of this system. Round up the availability to $5$ decimal places. $(10$ points$)$