In Pakistan, because of small field size, most often 2 or 3 rows windbreaks are used, and should expect the effects to reach only about 12H downwind and _____ upwind:

The correct answer to the question: "In Pakistan, because of small field size, most often 2 or 3 rows windbreaks are used, and should expect the effects to reach only about 12H downwind and _____ upwind:" is "2H".