A long-awaited audit of Maryland's health insurance exchange has found that the state improperly billed the federal government $28.4 million as former Gov. Martin O'Malley's administration struggled to launch what would become one of the most troubled websites in the nation. Though the year-long probe by the Department of Health and Human Services inspector general found no fraud or criminal wrongdoing, auditors said the state lacked oversight and internal controls — and they recommended that Maryland refund what the federal government paid to subsidize the cost of signing people up for coverage. The report — obtained by The Baltimore Sun...