Lice are a pesky problem for school aged children and is unrelated to cleanliness. The lifetimes of lice that have fallen off the scalp onto bedding is approximatley normally distributed with a mean of 2.2 days and a standard deviation of 0.4 days. We would expect that approximately 90% of the lice would die within about:
a. 3.9 days
b. 3.0 days
c. 2.5 days
d. 2.7 days
e. 2.6 days