I need help understanding this question, thank you:)

The length of human pregnancies from conception to birth varies according to a distribution that is approximately normal with mean 262 days and standard deviation 13 days. Use the 68-95997 rule to answer the following questions. (3) Between what values do the lengths of the middle 95% of all pregnancies fall? and days (b) How short are the shortest 2.5% of all pregnancies? days or less How long do the longest 2.5% of pregnancies last? days or more