In question 87, what is the 95 % confidence interval for the variance of the soda pumped into the cans?

Question 87

A soft drink producer installs a new assembly line to fill 12-oz soda cans.
After a week of operation, the plant manager randomly samples 120 cans of soda and weighs the soda. He finds that the soda cans contained an average of 12.05 oz of soda. The standard deviation of the weight is .02 oz. Construct a 95 % confidence interval for the average amount of soda pumped into the cans.