The Lundberg Survey monitors gas prices at gas stations nationwide. In a recent month, Lundberg reported that the average regular gas price for the stations it surveyed was $3.506 per gallon. Assume the population distribution of gas prices is normal. If the sample size was 20 stations and the standard deviation of gas prices in the sample was $.16,
a. Build a 95% confidence interval estimate of the average price of a gallon of gas for the population of gas stations nationwide.
b. If the size of the sample was 10 instead of 20, show the 95% confidence interval estimate.