Answer
a) 95%
b)68%
Work Step by Step
a) By the empirical rule, 95% of the data are within 2 standard deviations of the mean, hence the answer is 95%.
b) $|280-215|=|280-345|=65=standard \ deviation$, hence by the empirical rule, 68% of the data are within 1 standard deviation from the mean, hence the answer is 68%.
