Answer:
Three, but see below.
Explanation:
You can be certain of three, but that may not be true at all. The only way to know for certain is to put it into scientific notation.
4.05 * 10^5 would be three, but other answers are possible. For example
4.050 * 10^5 would have 4.
Electrons
although the conventional current is actually assumed to be a bunch of positive particles moving in the opposite direction

Since initial velocity is zero hence , u = 0
=> d = 1/2 * a * t2

on solving we get
d = 86.436 metres
Note ; Here Gravitational Acceleration is take as , g = 9.8 m/s2
V = S/t
The time is in minutes, it needs to be converted to seconds, because the Velocity 8.1meters/second.
1 min -------- 60 secs
8.5 min -------- x secs
-> x = 8.5 . 60
-> x = 510secs
-> 8.1 = S/510
-> 510 x 8.1 = S
-> S = 4131 meters