With usual assumptions we can calculate your answers with Erlang B as follows with E being the erlang b function and a the offered traffic:
Traffic carried on first circuit = a(1 – E(1,a)) Traffic carried on second cct= a(E(1,a) – E(2,a)) Traffic carried on third cct = a(E(2,a) – E(3,a)) Traffic carried on fourth cct= a(E(3,a) – E(4,a)) Traffic carried on fifth cct = a(E(4,a) – E(5,a))
The pattern continues.