U.S. energy use was approximately 100 quads (quadrillion Btu) in 2008. About 85% of this energy was supplied by burning fossil fuels (coal, oil, and gas). Assuming the average fuel composition and energy content are CH2 and 15,000 Btu/lb, respectively, calculate the U.S. contribution to global carbon emissions in 2008, Give your answer in Gt of carbon.