Solve the problem. Round results to an appropriate number of significant digits.
A plane is found by radar to be flying 5.2 km above the ground. The angle of elevation from the radar to the plane is 81.8°. Ten seconds later, the plane is directly over the station. Find the speed of the plane, assuming that it is flying level.
◦ 270 km/hr
◦ 290 km/hr
◦ 260 km/hr
◦ 280 km/hr