Prosecutors are investigating whether billionaire businessman Carl Icahn pushed for a federal policy change that would have benefited one of his investments while he was serving as an adviser to President Donald Trump. The U.S. attorney's office in Manhattan has issued subpoenas to Icahn's company and another company, CVR Energy, in which he has an 82 percent stake, both firms disclosed in regulatory filings. CVR is a publicly traded company that specializes in refining and is valued at nearly $3 billion. The companies said they are cooperating with the subpoenas, which were first reported by Bloomberg. "The U.S. Attorney's office...