Read the following (hypothetical) note and answer the questions as listed

BusinessWeek conducted a survey of graduates from 30 top MBA programs (BusinessWeek, September 22, 2003). The sample of 1,800 respondents had 987 female graduates. On the basis of the survey, assume that the mean annual salary for male and female graduates 10 years after graduation is $1.68mn and $1.17mn, respectively. Assume the standard deviation for the male graduates is $0.4 mn, and for the female graduates it is $0.25 mn

Construct the 95% confidence interval for proportion of males in the population.

Assuming a normal distribution, what is the probability that a female graduate will earn more than $ 1.75mn 10 years after graduation?

If the top 10% of the earners among males have to be identified, what should the annual salary cut off be?