The Mean Number of Travel Days Per Year for Salespeople

Multiple Choice

The mean number of travel days per year for salespeople employed by three hardware distributors needs to be estimated with a 0.90 degree of confidence. For a small pilot study,the mean was 150 days and the standard deviation was 14 days. If the population mean is estimated within two days,how many salespeople should be sampled?

A) 133
B) 452
C) 511
D) 2,100