7. Consider a single-server queuing system with FIFO service discipline and let X(t) be the number of customers in the system (including the customer in service). A simulation run for 180 minutes produced the following sample path (output) t-interval [0, 40) [40, 72) [72,83) [83, 96) [96, 129) (129, 136) (1) 0 1 2 1 2 1 t-interval [136, 148) [148, 165) [165, 175) [175, 180) [180,00) X (0) 2 3 2 1 0 (a) Compute an estimate of the mean number of customers in the system during [0, 180). 3 (b) Compute an estimate of the mean server utilization during [0, 180). (c) Compute an estimate of the mean customer delay in queue during [0, 180)