A Harris Poll asked Americans whether states should be allowed to conduct random drug tests on elected

Question:

A Harris Poll asked Americans whether states should be allowed to conduct random drug tests on elected officials. Of 21,355 respondents, 79% said “yes.”
a. Determine the margin of error for a 99% confidence interval.
b. Without doing any calculations, indicate whether the margin of error is larger or smaller for a 90% confidence interval. Explain your answer.