We consider a single repairman who maintains a coherent system of n components. Each component works for and is repaired in random periods of time with exponential distribution independent of the behavior of other components. We try to find a policy for assignment of the repairman which...

In this issue of the journal, Derman, Lieberman and Ross treat a replacement problem where several types (grades) of components are available. They conjecture than any component type that is more expensive to both purchase and to run than some other component type will never be used in an...