100 aaa batteries were tested on a particular mp3 player. suppose the battery has a mean lifetime of 31.7 hours, with a standard deviation of 2.9 hours. how long do we expect the majority of batteries to last? a. between 2.9 and 31.7 hours
b. between 28.8 and 31.7 hours
c. between 31.7 and 34.6 hours
d. between 28.8 and 34.6 hours