The monthly closing stock prices (rounded to the nearest dollar) for Panera Bread Co. for the first six months of 2010 are reported in 10 the following table. [You may find it useful to reference the t table.] Months Closing Stock Price January 120 3 February 125 points March 121 April 128 May 129 June 127 eBook Hint Source: http://finance.yahoo.com. Print a. Calculate the sample mean and the sample standard deviation. (Round intermediate calculations to at least 4 decimal places and References "Sample mean" and "Sample standard deviation" to 2 decimal places.) Sample mean Sample standard deviationeBook Hint b. Calculate the 99% confidence interval for the mean stock price of Panera Bread Co., assuming that the stock price is normally distributed. (Round "t" value to 3 decimal places and final answers to 2 decimal places.) Print ferences Confidence interval to c. What happens to the margin of error if a higher confidence level is used for the interval estimate? O The margin of error increases as the confidence level increases. O The margin of error decreases as the confidence level increases