A strength training program among marine recruits leads to an improvement in the number of push-ups completed in 5 minutes between the beginning and end of the program that is approximately normally distributed with a mean improvement of 9 push-ups (standard deviation = 3). What is the probability that a recruit improves by at least 12 push-ups? You may round to the nearest whole percentage point.

a.16%

b.50%

c.68%