U.S. consumers are increasingly viewing debit cards as a convenient substitute for cash and checks. The average amount spent annually on a debit card is $7,790 (Kiplinger's, August 2007). Assume that this average was based on a sample of 100 consumers and that the population standard deviation is $500.

a. At 99% confidence, what is the margin of error?

b. Construct a 99% confidence interval of the population mean amount spent annually on a debit card. P-69