The 1936 Summer Olympics in Berlin were the first Games to be broadcast on television, though only to local audiences. The 1956 Winter Olympics were the first internationally televised Olympic Games, and the 1960 Winter Olympics had their broadcasting rights sold for the first time to specialised television broadcasting networks—CBS paid US$394,000 for the American rights, and the European Broadcasting Union (EBU) allocated US$660,000. In the following decades the Olympics became one of the ideological fronts of the Cold War. Superpowers jockeyed for political supremacy, and the IOC wanted to take advantage of this heightened interest via the broadcast medium. The sale of broadcast rights enabled the IOC to increase the exposure of the Olympic Games, thereby generating more interest, which in turn created more appeal to advertisers time on television. This cycle allowed the IOC to charge ever-increasing fees for those rights. For example, CBS paid US$375 million for the American broadcast rights of the 1998 Winter Olympics, while NBC spent US$3.5 billion for the American rights of all the Olympic Games from 2000 to 2012. In 2011, NBC agreed to a $4.38 billion contract with the International Olympic Committee to broadcast the Olympics through the 2020 Summer Olympics, the most expensive television rights deal in Olympic history. NBC then agreed to a $7.75 billion contract extension on May 7, 2014, to air the Olympics through the 2032 games. NBC also acquired the American television rights to the Youth Olympic Games, beginning in 2014 Summer Youth Olympics, and the Paralympic Games for the 2014 Winter Paralympics and 2016 Summer Paralympics editions. NBC is one of the major sources of revenue for the IOC.
Question: How many more billions of dollars was NBC's contract extension signed on May 7, 2014 than their initial contract of $4.38 billion?
Answer: 3.37