General Motors Co posted a weaker-than-expected quarterly profit as weakness in South America and Russia hurt demand and the company's tax rate came in higher than expected. Net income in the first quarter rose to $945 million, or 56 cents a share, compared with $125 million, or 6 cents a share, a year earlier. Last year's results included charges related to recalls including a defective ignition switch. Excluding one-time items related to ending manufacturing in Russia and the compensation program related to the faulty switch, GM earned 86 cents a share. That was below the 97 cents analysts polled by Thomson Reuters I/B/E/S had expected. Revenue fell 4.5 percent to $35.7 billion, below the $37.6 billion analysts had expected. Weaker volume in Brazil and Russia hurt sales, as well as the impact of weakening currencies in South America due to the strong U.S. dollar. GM announced in March it would shut a Russian factory and wind down its Opel brand there due to slumping demand. (Reuters)