At the U.S. Open Tennis Championship a statistician keeps track of every serve that a player hits during the tournament.

[answerhappygod]

At the U.S. Open Tennis Championship a statistician keeps track
of every serve that a player hits during the tournament. The
statistician reported that the mean serve speed was 100 miles per
hour (mph) and the standard deviation of the serve speeds was 15
mph. If nothing is known about the shape of the distribution, what
percentage of the player's serve speeds are less than 70
mph?
A. approximately 5%
B. at most 11%
C. approximately 2.5%
D. at most 12.5%
E. at most 25%