Sears has had trouble staying afloat over the last several years and now CEO Eddie Lampert will open his wallet to help the struggling retailer. Lampert, a hedge fund manager, will offer a $200 million letter of credit to the department-store chain through affiliates of his firm, ESL Investments Inc. The amount could be expanded to as much as $500 million with the consent of lenders, according to a statement Thursday. Sears' stock rose as much as 8.7 percent after the letter of credit was announced. Sears lost more than 60 percent of its value this year before Thursday.