We Intend to Estimate the Average Driving Time of a Group

Multiple Choice

We intend to estimate the average driving time of a group of commuters. From a previous study, we believe that the average time is 42 minutes with a standard deviation of 7 minutes. We want
Our 90 percent confidence interval to have a margin of error of no more than plus or minus 4
Minutes. What is the smallest sample size that we should consider?

A) 9
B) 34
C) 3
D) 2