The professor doesn't offer help and I'm not getting any take aways from the book so I'm completely lost. I have no intention of submitting someone else work as my own I just need to know the steps to take to solve the problem.

A random sample of 26 items is drawn from a population whose standard deviation is unknown . The sample mean is * = 860 and the sample standard deviation is 5 = 20. Use Appendix @ to find the values of Student's*. ( a ) Construct an interval estimate of " with 95%6 confidence . ( Round your answers to 3 decimal places . ) The 95% confidence interval is from ?to [ (b ) Construct an interval estimate of u with 95% confidence , assuming that 5 = 40. ( Round your answers to 3 decimal places . ) The 95%6 confidence interval is from ? 1 to [ ( C ) Construct an interval estimate of " with 95%6 confidence , assuming that 5 = 80. ( Round your answers to 3 decimal places . ) The 95%6 confidence interval is from ? to [ (d ) Describe how the confidence interval changes as 5 increases . The interval stays the same as 5 increases ! The interval gets wider as 5 increases . O' The interval gets narrower as 5 increases