According to a study, 70 % of adult smokers started smoking before 21 years old. 8 smokers 21 years old or older are randomly selected, and the number of smokers who started smoking before 21 is recorded.

1. The probability that at least 4 of them started smoking before 21 years of age is

2.The probability that at most 3 of them started smoking before 21 years of age is

3. The probability that exactly 6 of them started smoking before 21 years of age is

Q2.Suppose (24,40) is a 90% confidence interval estimate for a population mean μ.

Margin of error =?