For this problem, carry at least four digits after the decimal in your calculations. Answers may vary slightly due to rounding. A random sample of medical files is used to estimate the proportion p of all people who have blood type B. (a) If you have no preliminary estimate for p, how many medical files should you include in a random sample in order to be 85% sure that the point estimate p will be within a distance of 0.04 from p? Find the critical value for 85% confidence level, Z0.85, and find the specified maximal error of estimate, E. (Round your answers to two decimal places.) 20.85 USE SALT = n = E = Compute the sample size n for estimating the proportion p of all people who have blood type B under these restrictions. (Round your answer up to the nearest whole number.) medical files (b) Answer part (a) if you use the preliminary estimate that about 15 out of 90 people have blood type B. (Round your proportions to three decimal places and your sample size up to the nearest whole number.)