Data from the Bureau of Labor Statistics’ Consumer Expenditure Survey show that annual expenditures for cellular phone services per consumer unit increased from $242 in 2001 to $619 in 2007. Let the standard deviation of annual cellular expenditure be $64 in 2001 and $204 in 2007. [You may find it useful to reference the z table.] a. What is the probability that the average annual expenditure of 109 cellular customers in 2001 exceeded $234? (Round "z" value to 2 decimal places, and final answer to 4 decimal places.)

b. What is the probability that the average annual expenditure of 109 cellular customers in 2007 exceeded $596? (Round "z" value to 2 decimal places, and final answer to 4 decimal places.)