Find the total annual gasoline consumption in the United States, along with the total area of the country's existing cropland. One study suggests that ethanol production from corn in the United States gives an annual yield of 71 GJ of ethanol energy per hectare (metric acre; 104 m2 ) of cropland. Use your findings, along with Table 3.3 to estimate the percentage of U.S. cropland that would be required to replace all U.S. gasoline with corn- based ethanol