A fixed resistor and a diode are joined in series to a battery with electromotive force (e.m.f.) $6.0\,\text{V}$ and negligible internal resistance. The graph shows how the current $I$ varies with potential difference (p.d.) $V$ for the diode. The current through the diode is $40\,\text{mA}$. What is the resistance of the fixed resistor?
- A$30\,\Omega$
- B$120\,\Omega$
- C$150\,\Omega$
- D$180\,\Omega$