Consider a Single-Server Queueing System with a Poisson Input,where the Server

Consider a single-server queueing system with a Poisson input,where the server must perform two distinguishable tasks in sequence for each customer,so the total service time is the sum of the two task times (which are statistically independent),where times are being expressed in units of a minute.(a)Suppose that the first task time has an exponential distribution with a mean of 3 minutes and that the second task time has an Erlang distribution with a mean of 9 minutes and with the shape parameter k = 3.Which queueing theory model should be used to represent this system? Also identify the parameters of the model.(b)Suppose that part (a)is modified so that the first task time also has an Erlang distribution with the shape parameter k = 3 (but with the mean still equal to 3 minutes).Which queueing theory model should be used to represent this system? Also identify the parameters of the model.