An aeroplane is flying at speed of 100 km/hr at a height of h km above the ground. At a particular instant, the angle of elevation from point A to the aeroplane is 60^∘. If aeroplane is moving away from point A then in the next 0.1 hr it will reach to point from which the angle of elevation from point A is 30^∘. Find the value of h. (in km)