A resistor X with resistance $40\,\Omega$ and a variable resistor are connected to a battery with electromotive force (e.m.f.) $12\,\text{V}$ and internal resistance $2.0\,\Omega$, as indicated. The resistance of the variable resistor is altered from $0$ to $40\,\Omega$. What is the change in power dissipated in resistor X?
- A$2.4\,\text{W}$
- B$2.7\,\text{W}$
- C$3.6\,\text{W}$
- D$5.6\,\text{W}$