Shares of Apple rallied on Friday, with the stock hitting a record after it was reported that Warren Buffett's company bought 75 million shares of the iPhone maker over the first quarter. The stock jumped 3.9%, bringing its week-to-date advance to 13.3%. That stands as the biggest one-week percentage gain for the Cupertino, Calif.-based tech giant since October 2011. Most of the stock's gains this week followed the release of its quarterly results on Tuesday, which trounced expectations. The Dow Jones Industrial Average rose 1.4% while the S&P 500 was up 1.3% and the Nasdaq Composite Index rose 1.7%.