Are you a little fuzzy on why it keeps getting more expensive to cross the Ben Franklin, Walt Whitman or George Washington bridges? So is Washington. The federal Government Accountability office — the GAO — is looking for answers.It’s asked bistate authorities on the Delaware and Hudson rivers, including the Delaware River Port Authority, to cooperate with the investigation — basically to explain how toll prices are set. Tim Ireland, spokesman for the DRPA, says to bring it on. “We welcome the scrutiny,” he said. “We will do everything we can to assist them. And we look forward to a productive collaboration in an initiative to make our workings more transparent.” In an email, Ned Griffith, spokesman for the GAO, said that recent toll increases have raised questions about whether transportation authorities are remaining accountable to their congressionally approved compact. He says they’ve just started to work and that it’s too early to say when they’ll issue a report.U.S. Sen. Frank Lautenberg of New Jersey called for the investigation.