Considering a system with its Reliability Block Diagram $($RBD$)$ illustrated below and assumingevery component works independently. The reliabilities of components $1,5,$and $6$ are given asR$=$ Rs$=$ R$6=0\mathrm{.}9,$the reliabilities of components $2,3,$and $4$ are given as R$2=$R$3=$R$4=0\mathrm{.}8,$ and the reliabilities of components $7,8,$and $9$ are given as R$,=$ RB$=$ Ro$=0\mathrm{.}7.$ As shownin the RBD$,$components $7,8,$ and $9$ works in the $2$ out of $3$ redundancy mode.