please help

Suppose that you live near a McDonald's restaurant and you want to estimate the proportion of all people in your neighborhood who go to McDonald's on a typical day. a. if you had no preliminary estimate, how many people should you include in a random sample to be 95% sure that the point estimate will be a distance of .05 from p? b, Answer part a if you use the preliminary estimate that nationally about 3 in 20 Americans goes to McDonald's every day