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 0.05 from p? (Round your answer up to the nearest whole number.)

(b) Answer part (a) if you use the preliminary estimate that about 9 out of 90 people have blood type B.