A random sample of 25 items is drawn from a population whose standard deviation is known to be σ = 40. The sample mean is x− = 270. (a) Construct an interval estimate for μ with 95 percent confidence. (Round your answers to 2 decimal places.) The 95% confidence interval is from to (b) Construct an interval estimate for μ with 95 percent confidence assuming that n = 50. (Round your answers to 2 decimal places.) The 95% confidence interval is from to (c) Construct an interval estimate for μ with 95 percent confidence assuming that n = 100. (Round your answers to 2 decimal places.) The 95% confidence interval is from to (d) Describe how the confidence interval changes as n increases. Width increases as n increases. Width decreases as n increases.