A subsidiary of Blackstone Group will buy Alliance Data Systems Corporation, a US credit card services firm, in a deal worth 7.8 billion dollars, Alliance said Thursday, according to dpa. Blackstone Capital Partners V LP will acquire all of Alliance's stock and take on its debts. Alliance shareholders will receive 81.75 dollars in cash per share, 30 per cent more than its value at close of markets Wednesday. The transaction is to be completed by the end of the year, pending the approval of shareholders and regulators. The Dallas, Texas-based firm works with 120 million customers and has 9,000 employees. Alliance earned 76.9 million dollars in the first quarter of 2007.