Security Pacific agreed to sell its trading system for over-the-counter options on U.S. Treasury notes to RMJ Securities for an undisclosed price . . . Media tycoon Rupert Murdoch has bought a half-share in the British arm of the U.S.-based general store group Circle K in a deal worth $36 million . . . Times Mirror announced the completion of its previously announced purchase of four consumer magazines from Diamandis Communications for $167.5 million and the assumption of deferred subscription liability. The Los Angeles-based media and information company also reported the completion of its sale of the Denver Post to Media News Group . . . Michael H. Fusco, a Los Angeles investor, said he sold his entire 6.2% stake in Olmstead, Kennedy & Gardner CapitalCorp.'s common shares outstanding due to a margin call.