Context: Various American Idol alumni had success on various record charts around the world; in the U.S. they had achieved 345 number ones on the Billboard charts in its first ten years. According to Fred Bronson, author of books on the Billboard charts, no other entity has ever created as many hit-making artists and best-selling albums and singles. In 2007, American Idol alums accounted for 2.1% of all music sales. Its alumni have a massive impact on radio; in 2007, American Idol had become "a dominant force in radio" according to the president of the research company Mediabase which monitors radio stations Rich Meyer. By 2010, four winners each had more than a million radio spins, with Kelly Clarkson leading the field with over four million spins.

Question: How many number one Billboard singles were released by American Idol contestants in the shows first decade? 
Answer: 345

Question: Who is the president of Mediabase? 
Answer: Rich Meyer

Question: Who was the most successful American Idol winner on radio as of 2010? 
Answer: Kelly Clarkson

Question: How many number ones have Idol singers achieved on Billboard charts in just the first ten years?
Answer: 345

Question: Who authored books on Billboard charts?
Answer: Fred Bronson

Question: How many contestants had at least one million radio spins by 2010?
Answer: four

Question: How many radio spins did Kelly Clarkson have by 2010?
Answer: over four million