Stocks moved higher in midday trading Monday, though cautiously after stellar gains last week marked the S&P 500's best five-day period of the year so far. A slump in commodities was keeping equities in check. Alcoa (AA) climbed on news hedge fund Elliott Management had taken a 6.5% stake in the aluminum producer. The fund said the company's plans to split its metal-making business from manufacturing would create shareholder value. Sales of previously-owned homes fell in October after a big jump in September. The decline was driven by a number of factors, most notably the discrepancy between rising home prices and stagnant wage growth. Mallinckrodt (MNK) jumped after the pharmaceutical company bested quarterly estimates.