70, 75, 80, 85, 90, 105, 105, 130, 130, 130.

The lists above consists of the times in seconds , it took each of 10 children to run a distance of 400m. If the standard deviation of the times is 22.4s, how many of the 10 running times are more than 1 standard deviation below the mean

a.1 b.2 c.3 d.4 e.5