1 will affect the school. Because according to Pythagorean theorem, the shortest distance from school A to the tractor route is 400/200 (the right angle side opposite to 30 degrees is half of the hypotenuse). 2. The noise is the biggest when the tractor runs for 200 (root number 3), and the time is 20 (root number 3) seconds. 3. The influence distance is 300 (as an auxiliary line), and the time is 30 seconds.