A startup company is interested in determining whether it's use of a blogger to advertise its product has increased sales. A random sample of buyers of the product found 57% of the 248 purchases heard about the product through the internet. After the blogger was hired, 70% of the 256 random sample of buyers heard about the product through the internet. What is the margin of error for a 99% confidence interval for the difference between the proportions of buyers who heard about the product from the internet.