Hi, need help with this this question

4 3. The personnel director of a large corporation wants to study absenteeism among clerical workers at the corporation's central office during the year. A random sample of 35 clerical workers reveals the following: [10 points] Absenteeism: X = 19.7 days, S= 5.0 days. 15 clerical workers were absent more than 12 days. a. Set up an 80 % confidence interval estimate of the average number of absences for clerical workers last year. b. Set up a 92% confidence interval estimate of the population proportion of clerical workers absent more than 12 days last year. c. If the personnel director also wants to take a survey in a branch office, what sample size is needed if the director wants to be 85% confident of being correct to within + 1.5 days and the population standard deviation is assumed to be 4.5 days? d. If the personnel director also wants to take a survey in a branch office, what sample size is needed if the director wants to be 90% confident of being correct to within + 0.075 of the population proportion of workers who are absent more than 12 days if the population proportion is known to be 0.45