3. The management of a local restaurant wants to determine the average monthly amount spent by households in fancy restaurants. Management wants to be 95-percent confident of the findings and does not want the error to exceed plus or minus $5.

a. After the survey was conducted, the average expenditure was found to be $90.30 and the standard deviation was $45. Construct a 95-percent confidence interval.

b. What sample size would have resulted in a standard deviation of $45?