Oil prices fell Monday to below $51 a barrel as investors engaged in profit-taking from oil's recent gains. Benchmark crude for May delivery was down $1.82 to $50.56 by midday in Europe in electronic trading on the New York Mercantile Exchange. The contract dropped $1.96 to settle at $52.38 on Friday. In London, Brent prices were down $1.56 to $50.42 a barrel on the ICE Futures exchange. Crude prices set 2009 highs last week, rising from $35 in February to close above $54 a barrel last Thursday, partly lifted by the recent rally in global stock markets.