According to the empirical rule, 68% of data will fall within 1 standard deviation from the mean. This means it will be either 39.8 lower than the mean or 39.8 higher than the mean: 685-39.8 = 645.2 685+39.8 = 724.8
d. since we know it can travel 500 mph and it has enough fuel to fly for another 1500 miles. it can fly for 3 more hours, the reason D is the correct answer is since the plane can't fly more than 3 hours so it will fly for 3 hours exactly or less
