We know that for a bell shaped distribution or normal distribution 68% of data fall within 1 standard deviation of the mean , 95% of data fall within 2 standard deviation of the mean and 99% of data fall within 3 standard deviation of the mean
we have mean = 10% and standard deviation = 15%
So, 68% of data will fall within
95% of data will fall within
99% of data will fall within
So, option B is correct because 95% of the data fall within -20% and 40%
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