Data from the Bureau of Labor Statistics'Consumer Expenditure Survey (CE) show that annual expenditures for cellular phone services per consumer unit increased from $210 in 2001 to $608 in 2007. Let the standard deviation of annual cellular expenditure be $48 in 2001 and $132 in 2007.

a. What is the probability that the average expenditure of 100 cellular customers in 2001 exceeded $200?

b. What is the probability that the average expenditure of 100 cellular customers in 2007 exceeded $600? L056