Kemper Corp. reported that it has lowered its stake in Gibraltar Financial Corp. to 14.07% of the common shares outstanding . . . AT&T and Quotron Systems said they have signed three contracts under which they formalized their marketing of an advanced information system for the financial services market . . . MCI reported that Kokusai Denshin Denwa Co. has decided to establish an operating relationship to provide long-distance telephone service from the United States to Japan with MCI International . . . Southmark Corp. reported that it has completed the acquisition of Carlsberg Corp. of Santa Monica for about $51 million in stock and cash.