This question: 1 point(s) possible 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 12.1. Complete parts (a) through (c). (a) Construct a 90% confidence interval for o? if the sample size, n, is 20. O The lower bound is 7.63 (Round to two decimal places as needed.) The upper bound is .(Round to two decimal places as needed.) (b) Construct a 90% confidence interval for o? if the sample size, n, is 30. The lower bound is (Round to two decimal places as needed.) The upper bound is . (Round to two decimal places as needed.) How does increasing the sample size affect the width of the interval? The width does not change O The width decreases O The width increases (c) Construct a 98% confidence interval for of if the sample size, n, is 20. The lower bound is .(Round to two decimal places as needed.)