A Sales Representative Has 600 Accounts

A sales representative has 600 accounts.He wants to take a random sample to determine the mean amount of yearly sales for these accounts.From past research,he knows that the population standard deviation is approximately $28,000.How large a sample should he take in order to estimate the population mean within $8,000 at a 98% level of confidence?

A) 60
B) 45
C) 75
D) 30