This is not a normal distribution problem but a binomial distribution problem. Number r of people in a sample of N in the age bracket is:

The sample size would have to be much larger than 8 for the use of the normal approximation to be valid, though the binomial calc gives a probability of 6.88% and the normal in this case 7.03%.

If you want to try the normal approximation calculation start by calculating the mean and standard deviation of the number of people in the given age group pulled over. Then you need to compute the probability using the normal distribution of between and .

CB