A simple random sample of size n is drawn from a population that is normally distributed. The sample mean, x, is found to be 109, and the sample standard deviation, s, is found to be 10. (a) Construct an 80% confidence interval about u if the sample size, n, is 21. (b) Construct an 80% confidence interval about u if the sample size, n, is 26. (c) Construct a 95% confidence interval about u if the sample size, n, is 21. (d) Could we have computed the confidence intervals in parts (a)-(c) if the population had not been normally distributed? Click the icon to view the table of areas under the t-distribution. (a) Construct an 80% confidence interval about u if the sample size, n, is 21. Lower bound: ; Upper bound: PM (Use ascending order. Round to one decimal place as needed.) le a h H ft