If this energy could be collected and converted to electrical energy with 25.0 % efficiency how large an area?

(in square kilometers) would be required to collect the electrical energy used by the United States? (1.0 X 10^19 joules per year). And iff the solar collectors were arranged in a square array, what would be the length of its sides in kilometers(km) and in miles(mi)? The sun transfers energy to the earth by radiation at a rate of approximately 1.00 kW per square meter of surface.