An $8\,\Omega$ resistor and a $4\,\Omega$ resistor are joined in series to a power supply. When a voltmeter is placed across the $8\,\Omega$ resistor, it shows $36\,\text{V}$. What reading will the voltmeter give if it is instead connected across the $4\,\Omega$ resistor?
- A$12\,\text{V}$
- B$18\,\text{V}$
- C$72\,\text{V}$
- D$108\,\text{V}$