need help with this problem: Two identical pellet guns are fired simultaneously from the edge of a cliff. These guns impart an initial speed of 20.2 m/s to each pellet. Gun A is fired straight upward

, with the pellet going up and then falling back down, eventually hitting the ground beneath the cliff. Gun B is fired straight downward. In the absence of air resistance, how long after pellet B hits the ground does pellet A hit the ground? It only gives 2- numbers but I need height?