A group controlled by New York investor Ivan F. Boesky said it raised its stake in Quotron Systems to 9.9% from about 7.4% . . . Maytag Co.'s $736-million acquisition of Magic Chef was approved by both companies' stockholders . . . Seagram Co.'s board of directors has authorized the purchase of about 4.7 million shares, or up to 5% of its common shares outstanding, following regulatory approval . . . Coffee futures prices plummeted to their lowest levels of the year on the Chicago Board of Trade amid rumors that Brazil was considering a price cut.