Suppose that a marketing research firm wants to conduct a survey to estimate the meanμof the distribution of the amount spent on entertainment by each adult who visits a certain popularresort. the firm would like to estimate the mean of this distribution to within $60 with 95% confidence. from data regarding past operations at the resort, it has been estimated that the standard deviation ofthe entertainment expenditures is no more than $400. how large does the firm’s sample size need to be?