A cell has an electromotive force (e.m.f.) of $8.0\,\text{V}$ and negligible internal resistance. It is included in a circuit, as shown. The reading $V_1$ is $4.0\,\text{V}$ and the reading $V_2$ is also $4.0\,\text{V}$. Calculate the resistance of resistor $R$.
- A$0.50\,\Omega$
- B$2.0\,\Omega$
- C$4.0\,\Omega$
- D$8.0\,\Omega$