Gayle Johnston, an employee of a mail order company, Call-Us, has two phone lines. She uses them to take calls from customers ordering products from the CallUs catalog. The typical call lasts 4 minutes, and she gets 10 calls per hour but both of these numbers are averages; times vary from call to call. A consultant, hired to study the process, has told Call-Us that both the time to serve a call and the time between incoming calls closely follows an exponential distribution. If a second caller phones, Gayle can ask the incoming call to "hold please" and then return to the current caller. If a third caller calls before she finishes the current call, then that call gets a busy signal. Call-Us worries about losing customers because of this type of event. They want to know if it makes sense to add additional phone lines and/or operators. An average caller places orders leading to profits of $24.76 for Call-Us and the cost of another line (rental and connect time) would work out to $4.00 per hour. Gayle is paid $12.00 per hour