In Part B, we determined that the ball takes about
2.8 sec to reach the vertex. Since the parabola is symmetric about the axis of symmetry, we know that it will take the same amount of time again to get back to the same height.
2.8×2=5.6
The player kicked it from ground level,
0 ft off the ground, so we know it will reach ground level again after
5.6 seconds.