Probabilities and Standard Deviations

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3. The computer club has 100 members. There are 50 women and 50 men. Thirty of the women are 21 years of age and older, 45 of the men are 21 years of age and older. What is the probability that a member who is 21 or older and selected at random will be a woman?

4.The mean salary for the engineering department of a large company is $100,000. The salaries for the engineering department follow a normal distribution. About 95% of the salaries are between $60,000 and $140,000. What is the standard deviation of the salaries for the engineering department?