A study of long distance phone calls made from the corporate offices of Pepsi Bottling Group, Inc., in Somers, New York, revealed the length of the calls, in minutes, follows the normal probability distribution. The mean length of time per call was 3.2 minutes and the standard deviation was 0.50 minutes.
(a) What fraction of the calls last between 3.2 and 4 minutes?
(b) What fraction of the calls last more than 4 minutes?
(c) What fraction of the calls last between 4 and 4.5 minutes?
(d) What fraction of the calls last between 3 and 4.5 minutes?