could you please help figure out the upper and lower bound. Thank you!

Score: 1.69 of 6 pts 4 of 6 (6 complete) HW Score: 62.87%, 10.69 of 17 pts *9.3.9 Question Help A simple random sample of size n is drawn from a population that is known to be normally distributed. The sample variance, s , is determined to be 13.1. Complete parts (a) through (c). (b) Construct a 90% confidence interval for o2 if the sample size, n, is 30. The lower bound is 8.93 . (Round to two decimal places as needed.) The upper bound is 21.45 . (Round to two decimal places as needed.) How does increasing the sample size affect the width of the interval? OO The width does not change The width increases The width decreases (c) Construct a 98% confidence interval for o2 if the sample size, n, is 20. The lower bound is . (Round to two decimal places as needed.)