If a ping pong ball falls from the top of a building that is 168 feet high , how many seconds will it take the ball to hit the ground ? the formula for distance is d=16t^2

Here given 'd' that is distance is 168 feet. we need to find seconds that is 't'.
from the given formula,
⇒ d=16 t²
⇒  = t²
⇒ t²= 
⇒ t²= 10.5
⇒ t=
⇒ t=3.24
thus the seconds required is 3.24 seconds

Answer is either b or c