Answer
Total flight plans fro cities B,C,D & E are:
{BCDE, BCED, BDCE, BDEC, BECD, BEDC, CDEB, CDBE, CEBD, CEDB, CBDE,CBED,DEBC, DECB, DBEC, DBCE, DCBE, DCEB, EBCD, EBDC, ECBD, ECDB, EDBC, EDCB}
We note that there are 12 plans with direct flight from B to C, therefore, excluding them we have 12 possible flight plans
Work Step by Step
As given in answer
