NEW YORK – Bank of America’s first-quarter profit fell more than 18 percent from a year earlier, hurt by weak performance in its trading unit. Its shares edged lower in premarket trading Thursday. BofA said trading revenue fell more than 15 percent to $3.3 billion as it made less money from investment banking fees. At its consumer banking unit, where the company makes most of its money, profit rose 22 percent to $1.79 billion.