A preliminary behavioral sutdy of the jingdong black gibbon, a primate endemic to the wuliang mountains in china, found that the mean song bout duration in the wet season is 12.59 mintues with a standard deviation of 5.31 miutes. assuming that song bout is normally distributed, determine the percentage of song bouts that have durations within
a. One standard deviation to either side of the mean
b. Two standard deviations to either side of the mean
c. Three standard deviations to either side of the mean