A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.01 with 90​% confidence...

A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.01 with 90​% confidence if ​(a) she uses a previous estimate of 0.38​? (b) she does not use any prior​ estimates?