Irina, standing on the edge of a cliff, throws a stone at a 40-degree angle above the horizontal with an initial speed of 10.0 m/s. The instant before the stone hits the ground below, it is traveling at a speed of 51 m/s. If Irina were to throw the other rock at a 40-degree angle below the horizontal from the cliff instead, with the same initial speed of 10.0 m/s, what is the magnitude of the velocity of the stone just before it hits the ground? Ignore any effects of air resistance.