8.83 Power for a similar significance test

Refer to Exercises 8.80, 8.81, and 8.82. Suppose you were planning a similar study for a different app. Assume that the population proportions are the same as the sample proportion in the Fox News study. The numbers of smartphone users will be the same for the before and after groups. Assume 80% power with a test using . Find the number of users needed for each group.