In a current election campaign, PSI has just found that 220 registered voters

In a current election campaign, PSI has just found that 220 registered voters, out of 500 contacted, favor a particular candidate.

a)      What’s the 95% confidence interval estimate for the proportion of the population of registered voters that favor the candidate?

b)      Suppose that PSI would like a .99 probability that the sample proportion is within + .03 of the population proportion. How large a sample size is needed to meet the required precision?  (A previous sample of similar units yielded .44 for the sample proportion.)