An airplane flies 120 km at a constant altitude in a direction 30.0° north of east. a wind is blowing that results in a net horizontal force on the plane due to the air of 2.40 kn in a direction 10.0° south of west. how much work is done on the plane by the air?

 Best   The net angle between the direction of flight of the aircraft and the wind in the opposing direction is 20. THe component opposing the aircraft is 2.4*cos 20 KN 
= 2400 * 0.9397 = 2255.2622 N. The distance covered is 120 Km 
The work done by the aircraft overcoming the wind is 
= 2255.2622 * 120000 = 270631464 = 2.71 x 10^8 N 
As the question is trickily worded as : the work done on the plane by the air (wind) the answer is -2.71 x 10^8 J . (fourth option)