A lossless transmission line with $0.2$ pu reactance per phase uniformly distributed along the length of the line, connecting a generator bus to a load bus, is protected up to $80\%$ of its length by a distance relay placed at the generator bus. The generator terminal voltage is $1$ pu. There is no generation at the load bus. The threshold pu current for operation of the distance relay for a solid three phase-to-ground fault on the transmission line is closest to:
1. $1.00$
2. $3.61$
3. $5.00$
4. $6.25$