$21.$ Six subsystem designs have been proposed for a critical part

of a communications network. Each will be 'burned in$*$ to

eliminate the Infant mortality problem. Hence, reliability of the

subsystem will have a constant hazard rate. That Is$,$ the failure

density function will be exponential and reliability may be

expressed as

M t$)=$ e $-$U

where t Is the mission time. Mission time for the subsystem will

be one year, as a thorough annual preventative maintenance

and recalibration procedure Is standard, returning the

subsystem to 'new$*$ condition. The unit will be on call $24$ hours

a day, seven days a week. The design data are as follows:

$328$ Chapters

System

Annual Equivalent

Initial Cost

Annual

Maintenance Cost X

A $ $9000$ $$17001\mathrm{.}1446886$ IO$"6$

B $980014001\mathrm{.}098901110"*$

C $1020018001\mathrm{.}17582410"6$

D $1100013001\mathrm{.}07000010-5$

E $1100015001\mathrm{.}081250$ IO$"4$

F $131009000\mathrm{.}998000$ IO$-5$

Using cost$-$effectiveness analysis, plot reliability versus annual

cost Which subsystems can be eliminated from consideration?

How might you decide among the rest? $(6\mathrm{.}8)$