Rex Tillerson’s disclosure that he stands to receive a $180 million cash payout from Exxon Mobil Corp. if he becomes the next U.S. secretary of state offers a preview of the thorny ethical questions that may be raised this week over a presidential cabinet stacked with tycoons. And with confirmation hearings scheduled for Tillerson and eight other appointees of President-elect Donald Trump, the head of the federal office that helps ensure compliance with conflict-of-interest rules told lawmakers his agency is hard-pressed by too much work and too little time.