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9.23 An engineer designs a system consisting of two subsystems in series. The reliabilities are R, = 0.98 and R, = 0.94. The cost of the two subsystems is about equal. The engineer decides to add two redundant components, Which of the following would it be better to do? (a) Duplicate subsystems 1 and 2 in high-level redundance. (b) Duplicate subsystems 1 and 2 in low-level redundance. (c) Replace the second subsystem with 1/3 redundance. Justify your