Use the data in Example 20.2. But now suppose that 10% of Cast Iron's customers are slow payers and that slow payers have a probability of 30% of defaulting on their bills. If it costs $5 to determine whether a customer has been a prompt or slow payer in the past, should Cast Iron undertake such a check? (What are the expected savings and expected profit from the credit check? The answers will depend on both the probability of uncovering a slow payer and the savings from denying slow payers credit.)