Answer:
11
Explanation:
According to the empirical rule, 95% of data in a normal distribution will be between 2 standard deviations below the mean and 2 standard deviations above the mean.
Therefore, 2 standard deviations above the mean would be 21+2(5)=21+10=31 and 2 standard deviations below the mean would be 21-2(5)=21-10=11.
Thus, the lower value is 11