Data from the Bureau of Labor Statistics' Consumer Expenditure Survey show that annual expenditures for cellular phone services per consumer unit increased from $222 in 2001 to $620 in 2007. Let the standard deviation of annual cellular expenditure be $36 in 2001 and $157 in 2007 a. What is the probability that the average annual expenditure of 109 cellular customers in 2001 exceeded $213? (Round answer to 4 decimal places.) Probability b. What is the probability that the average annual expenditure of 109 cellular customers in 2007 exceeded $615? (Round answer to 4 decimal places.) Probability