Building the the discussion of probability distributions in Module 3, we apply this knowledge to a specific application: the design of extended service warranty plans. We provide an overview of the business problem and discuss how to incorporate uncertainty in customers' use of the warranty plan using the Poisson distribution. Using Microsoft Excel, we design a spreadsheet tool that enables a user to adjust features of the service plans. By comparing firm profit under different scenarios, we investigate how different features of the service plan result in risk being shared by the consumer and the firm.