TOKYO (Reuters) – Sony Corp slashed its operating profit estimate by nearly 70 percent for the financial year ended March 31, saying it saw an additional 30 billion yen ($293.7 million) in costs from exiting the PC business. The Japanese consumer electronics giant on Thursday cut its operating profit forecast to 26 billion yen from a previous estimate of 80 billion yen, adding that it would book 25 billion yen in impairment losses from its overseas disc production unit for fiscal 2013. Sony also cut its net loss forecast to 130 billion yen from a previous forecast of 110 billion yen. ($1 = …