4. (a) An analyst wishes to estimate the average annual expenditures per company on high-end coffee maker machine. The estimate must be accurate within plus or minus $80 and the estimated standard deviation in such expenditures is $400. For a 90% confidence interval, what is the required sample size? (Hint: use standard normal table or Excel. You can round up or down to the nearest integer.) (b) On a separate study, this analysis is studying the annual expenditures per company on coffee filter. Through a survey, he collected a sample and observed the following information from that sample: minimum expenditure observed = $600, maximum expenditure observed = $1,100, average expenditure (based on sample) = $1,050. What is an approximate estimate for standard deviation of population for the annual expenditures on coffee filter