What's the best way to solve this ?

A local men's clothing store is being sold. The buyers are trying to estimate the percentage of items that are outdated. They will choose a random sample from the store's inventory in order to determine the proportion of merchandise that is outdated. We want our 95% confidence interval to have a margin of error of no more than plus or minus 5%. How large of a sample do the buyers need? Hint: Don't forget that if you are using the formulas, your answer should be a whole number, rounded up