Use the Empirical Rule. The mean speed of a sample of vehicles along a stretch of highway is 69 miles perhour, with a standard deviation of 3 miles per hour. Estimate the percent of vehicles whose speeds are between 66 miles per hour and 72 miles per hour.(Assume the data set has abell-shaped distribution.)

Approximately _______ of vehicles travel between 66 miles per hour and 72 miles per hour.