A restaurant owner wishes to find the 80% confidence interval of the true mean cost of a green salad. How large should the sample be if she wishes to be accurate within 0.15? A previous study showed that the standard deviation of the price was $0.846. Please show all your work and if you use a calculator shortcut state what you entered as I'm really trying to learn how to use the calculator. round the same place value as the statistic given. Thank you