context: Guinness World Records lists Christie as the best-selling novelist of all time. Her novels have sold roughly 2 billion copies, and her estate claims that her works come third in the rankings of the world's most-widely published books,[6] behind only Shakespeare's works and the Bible. According to Index Translationum, she remains the most-translated individual author, having been translated into at least 103 languages.[7] And Then There Were None is Christie's best-selling novel, with 100 million sales to date, making it the world's best-selling mystery ever, and one of the best-selling books of all time.[8] Christie's stage play The Mousetrap holds the world record for longest initial run. It opened at the Ambassadors Theatre in the West End on 25 November 1952, and as of September 2018 is still running after more than 27,000 performances.[9][10]
question: How many units has Agatha Christie sold?
answers.text: 2 billion 2 billion copies 2 billion copies