Explain how the probability of blocking in a telecommunications system is defined using each of the following two assumptions. i) Blocked calls are lost. ii) Blocked calls are held. Assuming that blocked calls are lost, calculate the grade of service if 100 subscribers share 5 transmission channels, and each subscriber generates 0.04 Erlang of traffic. Find the number of channels required to improve the grade of service to 1% or better. • Given that the average time of a call is 72 second. Find the number of calls lost due to blocking during the busiest hour using the improved system.