The area of the U.S. is about 3.907 million square miles. Approximately 680000 square miles are worked for food production. What percent of the U.S. is worked

The area of the U.S. is about 3.907 million square miles. Approximately 680000 square miles are worked for food production. What percent of the U.S. is worked for food production? 
Round your answer to the nearest tenth of a percent.