According to a study, 90 % of adult smokers started smoking before 21 years old. 9 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 7 of them started smoking before 21 years of age is
2. The probability that at most 5 of them started smoking before 21 years of age is
3. The probability that exactly 8 of them started smoking before 21 years of age is