II-A city wants to know if a new advertising campaign to make citizens aware of the dangers of driving after drinking has been effective. They count the number of drivers who have been stopped with more alcohol in their systems than the law allows for 25 days before and 25 days a month after the campaign started. Letbe the difference between the number of drivers caught with excessive alcohol in their systems before and after the campaign on any given day. Treat these as a random sample from a Normaldistribution.

Information collected randomly during the 25 days before and the 25 days a month after the campaign, indicate a mean difference, and a standard deviation.

2a)Obtain a 95% confidence interval for the true average difference in number of drivers stopped with excess alcohol in their systems.