Pretzels: In order to judge the effectiveness of an advertising campaign for a certain brand of pretzel, a company obtained a simple random sample of 100convenience store receipts the week before the ad campaign began, and found that 21 of them showed a purchase of the pretzels. Another simple random30sample of 80 receipts was taken the week after the ad campaign, and of them showed a pretzel purchase.Part: 0/2Part 1 of 2(a) Construct a 99.9% confidence interval for the difference between the proportions of customers purchasing pretzels before and after the ad campaign.Let P? denote the proportion of customers purchasing pretzels before the ad campaign. Use tables to find the critical value and round the answer to atleast three decimal places.A 99.9% confident that the difference between the proportions of customers purchasing pretzels before and after the adcampaign is