Answer:
10.1 s
Explanation:
The time of flight of the package is entirely determined by its vertical motion, which is a free fall motion (it is acted upon the force of gravity only). Therefore, it is a uniformly accelerated motion, so we can use the suvat equation:

where
s is the vertical distance covered
u is the initial vertical velocity
t is the time of flight
is the acceleration due to gravity
For the package in this problem, we have:
s = 500 m is the vertical distance covered
u = 0 is the initial vertical velocity (initially it has only horizontal motion)
So, solving for t, we find the time of flight:
