OSLO (Reuters) – A $6 cardboard box that uses solar power to cook food, sterilize water and could help 3 billion poor people cut greenhouse gases, has won a $75,000 prize for ideas to fight global warming. The "Kyoto Box," named after the United Nations' Kyoto Protocol that seeks to cut emissions of greenhouse gases, is aimed at billions of people who use firewood to cook. Costing 5 euros ($6.60) to make, it can also make it easier to boil polluted water. "We're saving lives and saving trees," the Kyoto Box's developer Jon Boehmer, a Norwegian based in Kenya, said...