Consider a simple call center. $$ On average $3$ calls arrive every $15$ minutes. Assume inter$-$arrival times follow exponential distribution. $$ Average service time $=90$ seconds with standard deviation $=120$ seconds. $$ Calculate: $-$ average waiting time in queue $($Tq$)-$ average flow time $($T$)($in the process$)-$ flow rate $($$)-$ average queue length $($inventory$)($Iq$)-$ average number of calls in service $($Is$)-$ average number of call in the process $($I$)$