What is the Federal rules of civil procedure to file or serve the answer to a complaint?

Under the Federal Rules of Civil Procedure, a defendant must file their answer to a complaint within 21 days after being served with the summons and complaint, or 60 days if the defendant has waived service of process. The answer must be filed with the court and served on the plaintiff, containing responses to each allegation in the complaint and any affirmative defenses. If a defendant fails to respond within this timeframe, they may be subject to a default judgment.