Suppose the cost of a full-page color ad in the U. S. national edition of The Wall Street Journal (newspaper) is $327,897 and its U. S. audience size is 1,566,027. The cost of a full-page color ad in the U. S. national edition of Sports Illustrated (magazine) is $396,600 and has an audience size of 3,000,000. The cost of a 30-second ad on the most recent Super Bowl telecast is $3,800,000 and has an audience size of 108,400,000. Using this information, which metric should be used to determine the most efficient medium would