In order to set rates, an insurance company is trying to estimate the number of sick days that full time workers at an auto repair shop take per year. A previous study indicated that the standard deviation was 2.2 days. a) How large a sample must be selected if the company wants to be 98% confident that the true mean differs from the sample mean by no more than 1 day? b) Repeat part (a) using a 99% confidence interval. Which level of confidence requires a larger sample size? Explain.