Airplanes A and B are flying with constant velocity in the same vertical plane at angles
30∘ and
60∘ with respect to the horizontal respectively as shown in the figure. The speed of A is
100√3 m/s. At time t = 0s, an observer in A finds B at a distance of 500m. The observer sees B moving with a constant velocity perpendicular to the line of motion of A. If at
t=t0, A just escapes being hit by
B,t0 in seconds is
.