If mean is 20, the values 2.5 standard deviations away from mean will be
20 + 2.5(3) and 20 - 2.5 (3)
27.5 and 12.5.
So, anything greater than 27.5 and less than 12.5 is more than 2.5 SDs away from mean.
Hence A, 12.0
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