Stochastic Behaviour of a Special Complex System

The system has three subsystems: A, B, C. A has several non-identical units in series. B has 2 identical units in parallel. C has 2 identical units in standby (cold) redundancy. Switching is perfect. Unit failure rates are constant, repair rates need not be constant. The system fails if A or B fails; C is useful, but not essential. The supplementary variable technique is used to find Laplace transforms of system state probabilities.