Could you please provide step-by-step explanation for the answers of the following questions.

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26 . A sample of 35 different payroll departments found that employees worked an average of240 . 6 days a year . If the population standard deviation is 18 8 days ,a ) find the point estimate of the population meanAns : Point estimate : 240 6 daysb / find the 90% confidence interval for the average number of days " worked by allemployees who are paid through payroll departmentsAnS : 235 4 5 45 245 8