A pilot must fly his plane to a town which is 200km from his starting point in a direction 30degrees N of E. He must make the trip in 1/2 h. An 80km/h wind blows in a direction 30degrees E of S. Find the speed of the plane relative to air.

I found the speed of the plane relative to the ground is 400km/h.

The answer for the speed of the plane relative to the air is 408 km/h. Can someone please explain HOW you would get that. I've spent much too mlong trying to figure it out myself and it just doesnt make any sense. Thanks so much