Answer:
313.6 m downward
Step-by-step explanation:
The distance covered by the bullet along the vertical direction can be calculated by using the equation of motion of a projectile along the y-axis.
In fact, we have:

where
y(t) is the vertical position of the projectile at time t
h is the initial height of the projectile
is the initial vertical velocity of the projectile, which is zero since the bullet is fired horizontally
t is the time
a = g = -9.8 m/s^2 is the acceleration due to gravity
We can rewrite the equation as

where the term on the left,
, represents the vertical displacement of the bullet. Substituting numbers and t = 8 s, we find

So the bullet has travelled 313.6 m downward.