A market research firm supplies manufacturers with estimates of the retail sales of their products from samples of retail stores. Marketing managers are prone to look at the estimate and ignore sampling error. An SRS of 1414 stores this year shows mean sales of 6161 units of a small appliance, with a standard deviation of 6.66.6 units. During the same point in time last year, an SRS of 1414 stores had mean sales of 53.27853.278 units, with standard deviation 10.210.2 units. An increase from 53.27853.278 to 6161 is a rise of about 13%. 1. Construct a 99% confidence interval estimate of the difference 1212, where 11 is the mean of this year's sales and 22 is the mean of last year's sales.