consider a two stage line with buffer of capacity 4 between the 2 stages. Stage 1 is either operational or under repair. It falls with probability a1 in a cycle when working. Stage 2 fails gradually. With probability alpha24 it goes from operational to partially failed on a cycle. If partially failed in transitions to state failed with probabilty alpha26 in a cycle. If a station is failed, it is repaired with with a probability beta in a cycle. Station 2 can operate when it is operational or partially failed (but an inspector is added to check the finished product when stage 2 is in the partially failed state) The system is currently in state (WS1 operational, 3 in buffer