Answer:
See below
Step-by-step explanation:
Vertical component of the kick-off velocity is 8.4 sin21° = 3.01 m/s
Find the time-point where vertical velocity = 0 the ball is in the air for twice this long ( as it still has to fall back down to the ground)
vf = vo + at
0 = 3.01 m/s - 9.81 t shows t = .307 twice this is .614 sec
( what a sorry kick !)