4. In a data communications network, messages arrive to be transmitted over a particular link. The average time required to transmit a message is 0.6 seconds and the transmit time is exponential distributed. Messages arrive according to a Poisson process with rate 1 message per second.
(a) How long in average does each message has to spend to be transmitted through the link?
(b) What is the probability that a message can be transmitted through the link in 5 seconds?
(c) What is the 95% percentile of the number of messages in the link?