At a single$-$phase, multiple$-$channel service facility, customers arrive randomly. Statistical analysis of past data shows that the interarrival time has a mean of $10$ minutes and is exponentially distributed. The service time per customer has a mean of $4$ minutes and is exponentially distributed. The arrival buffer capacity is $4$ customers. The lost customer cost due to blocking is $$100$ per customer. The waiting cost is $$50$ per customer per hour. The server cost is $$15$ per server per hour. The table below is the Performance xls spreadsheet which is used to generate the calculations when we have $1,2,$ or $3$ servers in the system. We are trying to determine the operating cost of each system.