Calculate the equivalent resistance \( R_{\text{eq}} \):
\[ R_{\text{eq}} = 4000 \, \Omega \]
Calculate the current:
\[ i = \frac{4}{4000} = \frac{1}{1000} \, \text{A} \]
Then,
\[ V_0 = \frac{1}{1000} \times 500 = 0.5 \, \text{V} \]
The current passing through the battery in the given circuit, is: