Based on a representative sample of 511 U.S. teenagers age 12 to 17, International Communications Research estimated that the proportion of teens who support keeping the legal drinking age at 21 is p^ = 0.64 (64%). The press release titled “Majority of Teens (Still) Favor the Legal Drinking Age” (www.icrsurvey.com, January 21, 2009) also reported a margin of error of 0.04 (4%) for this estimate. Show how the reported value for the margin of error was computed.