The times for the mile run of a large group of male college students are approximately Normal with mean 7.11 minutes and standard deviation 0.74 minutes. Using the 68-95-99.7 rule, about what percent of these men run a mile in less than 6.37 minutes?
a. 2.5%
b. 5.0%
c. 16.0%
d. 32.0%