Erlang B calculator

This is a traditional Erlang B calculator. It can be used to work out the number of voice lines which need to be engineered in a trunk group, if the busy hour traffic (in Erlangs) offered to that trunk group is known. The calculator takes one parameter: blocking is the percentage of calls which will be blocked (receive a busy signal), because an insufficient number of lines have been provided. The default value for blocking is 0.01 (1%).