4.8 System reliability. A system consists of n mutually independent subsystems whose service times Xi's have identical PDF f (ac) = Ae'muc). Find the CDF of the service time X of the system if the subsystems are connected (a) in series, (b) in parallel, (c) in series of 71/2 pairs of subsystems with each pair connected in parallel, and (d) in parallel of two groups, each consisting of 71/2 subsystems connected in series