An aeroplane is flying horizontally at a height of 1.8 km above the ground. The angle of elevation of a plane from point X is 60° and after 20 seconds, its angle of elevation from X becomes 30°. If point X is on the ground, then what is the speed (in km/hr) of the aeroplane?
1
216√3
2
105√3
3
201√3
4
305√3