I want to know the answer to the following question:
In what year did Pfizer's patent over Lipitor expire?
All the background I'm provided with is that "The top ten best-selling drugs of 2013 totaled $75.6 billion in sales, with the anti-inflammatory drug Humira being the best-selling drug worldwide at $10.7 billion in sales.". Is that enough to answer the question?
Answer: no