An aeroplane flying horizontally at a height of 3 km. above the ground is observed at a certain point on earth to subtend an angle of 60°. After 15 sec flight, its angle of elevation is changed to 30°. The speed of the aeroplane (taking √3 = 1.732) is:
1
230.63 m/sec
2
230.93 m/sec
3
235.85 m/sec
4
236.25 m/sec