A physical therapist wants to determine the difference in the proportion of men and women who participate in regular sustained physical activity. What sample size should be obtained if he wishes the estimate to be within four percentage points with 99% confidence, assuming that (a) he uses the estimates of 22.1% male and 19.2% female from a previous year? (b) he does not use any prior estimates? (a) n = (Round up to the nearest whole number.) (b) n = (Round up to the nearest whole number.)