1) Past records indicate that each of the 5 laser computer printers at the U.S. Department of Energy, in Washington, DC, needs repair after about 20 hours of use. Breakdowns have been determined to be Poisson distributed. The one technician on duty can service a printer in an average of 2 hours, following an exponential distribution. Printer downtime costs $120 per hour. Technicians are paid $25 per hour. Should the DOE hire a second technician?
2) Joe Ferris is a stock trader on the floor of the New York Stock Exchange for the firm of Smith, Jones, Johnson, and Thomas, Inc. Stock transactions arrive at a mean rate of 20 per hour. Each order received by Joe requires an average of two minutes to process.
A) What is the mean service rate per hour?
B) What percentage of the orders will be processed in exactly 3 minutes?
C) What is the average time an order must wait from the time Joe receives the order until it is finished being processed (i.e. its turnaround time)?
D) What is the average number of orders Joe has waiting to be processed?
E) What percentage of the time is Joe processing orders?