A study of long distance phone calls made from General Electric
A study of long-distance phone calls made from General Electric Corporate Headquarters in Fairfield, Connecticut, revealed the length of the calls, in minutes, follows the normal probability distribution. The mean length of time per call was 4.2 minutes and the standard deviation was 0.60 minute.
a. What fraction of the calls lasts between 4.2 and 5 minutes?
b. What fraction of the calls lasts more than 5 minutes?
c. What fraction of the calls lasts between 5 and 6 minutes?
d. What fraction of the calls lasts between 4 and 6 minutes?
e. As part of her report to the president, the director of communications would like to report the length of the longest (in duration) 4% of the calls. What is this time?

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