Mathematics Homework Help

Annual starting salaries for college graduates with degrees in business administration are generally expected to be between $30,000 and $45,000.  Assume that a 95% confidence interval estimate of the population mean annual starting salary is desired.  What is the planning value for the population standard deviation?  How large a sample should be taken if the margin of error is
a. $500?
b. $200?
c. $100?
d. would you recommend trying to obtain the $100 margin of error?  Explain.