News roundup: Falling gas prices hurts big oil’s push for U.S crude exports … Holder confirms investigation into Target data breach … Study finds Affordable Care Act will have big impact on income gap

Supply and demand: A push by big oil companies such as Exxon Mobil Corp. and ConocoPhillips to export U.S. oil overseas is facing a new obstacle: falling gasoline prices. As Bloomberg reports, the flo…