Teletraffic engineering/Blocking/Answer1

We have first to find the busy-hour traffic. BHT = 167 Erlangs using Little's Rule.

According to Little's Rule: For the hour, the traffic in Erlangs = $\frac{N u m b e r o f c a l l s * M e a n H o l d i n g T i m e (s e c o n d s)}{3600}$

Using the Erlang-B formula is cumbersome in this example because there are many circuits. An Erlang-B calculator is used instead. The Blocking Probability is found to be 0.021 (2.1%)