An employee fits a door to an AGA 3-Oven Classic range cooker at the company's plant in Telford, U.K. Whirlpool Corp. started a takeover contest for Aga Rangemaster Group Plc by challenging an agreed 129 million-pound bid for the British ovenmaker from fellow U.S. company Middleby Corp. Aga shares rose as much as 12 percent after the U.S. appliances maker said it approached the U.K. company about a possible cash offer. Aga Rangemaster, best known for its heavy-duty cast iron stoves that cost about 2,000 pounds, accepted a bid from cooking-equipment maker Middleby in July.