In a study of cell phone service released by J.D. Power and Associates in 2012 (source: jdpower.com), the aver-age time that customers who called their cell phone company were put on hold before they were able to speak to a customer service representative was 4.6 minutes. Assume the distribution of hold times is normal, with a standard deviation of 1.2 minutes.
a. What percentage of customers experienced a hold time greater than 6 minutes?
b. What percentage of customers experienced a hold time between 3 and 5 minutes?
c. 80% of the customers were on hold for between _____ minutes and _____ minutes. (Make your interval symmetric around the mean.)
d. 50% of the customers were on hold for between 3.5 minutes and ____ minutes.