Consider in figure below with a server$-$client cluster with an active$-$takeover configuration between

two identical servers. The servers share a disk via a SCSI bus. The clients $($PCs or workstations$)$ and

the Ethernet are fail$-$free. When a server fails, its workload is switched to the surviving server

$$Assume that each server has an MTTF of $200$ days and an MTTR of five days. The disk has an

MTTF of $800$ days and an MTTR of $20$ days. In addition, each server is shut down for maintenance

for one day every week, during which time that server is considered unavailable. Only one server is

shut down for maintenance at a time. The failure rates cover both natural failures and scheduled

maintenance. The SCSI bus has a failure rate of $2$ percent. The servers and the disk fail

independently. The disk and SCSI bus have no scheduled shutdown. The client machine will never

fail.

a$.$ The servers are considered available if at least one server is available. What is the combined

availability of the two servers?

solve this step by step and give the answer