A boy is running along a straight horizontal road with a constant speed \(5\,\text{m s}^{-1}\). While running he throws a stone with a velocity \(30\,\text{m s}^{-1}\) at an angle \(60^\circ\) with the horizontal. Then the time of flight of the stone is: (Given \(g = 10\,\text{m s}^{-2}\))