Assume that originally u. s. gdp is $10 trillion, but that the economy is closed and there are no imports or exports. the nation of twinsylvania begins selling high-quality yard tractors in the united states but charges a very low price—say, $70 each. assume that u. s. consumers use this opportunity to buy yard tractors from twinsylvania instead of u. s.-produced yard tractors, and that spending on other u. s. goods does not change.