Two boys conducted experiments on the projectile motion with stopwatch and noted some readings. As one boy throws a stone in air at the same angle with the horizontal, the other boy observes that after \(4 \mathrm{~s}\), the stone is moving at an angle \(30^{\circ}\) to the horizontal and after another \(2 \mathrm{~s}\) it is travelling horizontally. The magnitude of the initial velocity of the stone is (Acceleration due to gravity, \(g=10 \mathrm{~ms}^{-2}\).)

1. A \(40 \sqrt{3} \mathrm{~ms}^{-1}\)
2. B \(20 \sqrt{3} \mathrm{~ms}^{-1}\)
3. C \(10 \sqrt{3} \mathrm{~ms}^{-1}\)
4. D \(50 \sqrt{3} \mathrm{~ms}^{-1}\)