suppose the cpa practice advisor reports that the mean preparation fee for 2017 federal income tax returns was $273. use this price as the population mean and assume the population standard deviation of preparation fees is $100. (a) what is the probability that the mean price for a sample of 20 federal income tax returns is within $16 of the population mean? (round your answer to four decimal places.) (b) what is the probability that the mean price for a sample of 60 federal income tax returns is within $16 of the population mean? (round your answer to four decimal places.) (c) what is the probability that the mean price for a sample of 81 federal income tax returns is within $16 of the population mean?(round your answer to four decimal places.) (d) which, if any, of the sample sizes in parts (a), (b), and (c) would you recommend to ensure at least a 0.95 probability that the sample mean is within $16 of the population mean? (select all that apply.)