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 she wishes the estimate to be within three percentage points with 90% confidence, assuming that (a) she uses the estimates of 21.5% male and 19.7% female from a previous year? (b) she does not use any prior estimates? (a) n = 983 (Round up to the nearest whole number.) (b) n = (Round up to the nearest whole number.)