By Brian A. Shactman, CNBC Reporter
NEW YORK ( CNBC) -- It is time to ask and answer the question once again: Who is Tim Cook? With Apple ( AAPL) CEO Steve Jobs stepping back for an unknown amount of time, Cook is stepping in for the third time since he joined Apple in 1998. The last time this happened was two years ago. In mid-January of 2009, Jobs took leave, and Cook took the post of interim CEO. Initially, the stock sold off about 10 percent. That loss was reversed within days, and in the six months that Jobs was dealing with a liver transplant, the stock rose 70 percent, far outpacing the broader indexes.
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