Calls requiring information technology (IT) support arrive at the help desk every 3 minutes (exponential distribution). The time it takes to troubleshoot the problem over the phone is exponentially distributed with a mean of 6 minutes. IT support staff is paid an average of $25 an hour. The lost time for the care provider making the call to have the issue resolved is valued at $70 an hour. Based on a cost analysis, what is the optimal number of servers?