Answer
The current through the person is $~~3600~A$
Work Step by Step
Let the resistance through the air along the tree be $R$
Then the resistance through the air to the person is $0.4~R$
Note that the potential difference is the same for either path.
Let $i_p$ be the current through the person.
Note that the current along the tree is $5000-i_p$
We can find $i_p$:
$\Delta V = (i_p)(0.4~R) = (5000-i_p)(R)$
$1.4~i_p = 5000$
$i_p = \frac{5000}{1.4}$
$i_p = 3600~A$
The current through the person is $~~3600~A$
