A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall. 15 credit card accounts...

A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall.  15 credit card accounts  randomly sampled produced a mean of $50.50 and a variance of 400.  A 95% confidence interval for the average amount the credit card customers spent on their first visit to the chain's new store in the mall is: