please explain how to solve, I need explanations for all questions.

Question 1: Forz/2=2.57, what is the value of ?

Question 2: What is the confidence level for the interval for the z-value in Question 1?

Question 3:For a 95% confidence interval for when the sample size is 100 and the sample mean is 58.3.

Find z/2

For a 95% confidence interval for when the sample size is 100 and the sample mean is 58.3.=3.0

Question 4: Compute the 95% confidence interval.