We want to install an electric bell. The ringing location is 30 meters away from the bell. The internal resistance of the bell is 2 ohms. We intend to use 2 series-connected Leclanché cells as the power source, each with an electromotive force of 1.5 Volts and an internal resistance of 1 ohm. What diameter copper wire should we use, if the bell only works reliably when at least 0.4 amperes flow through it. The resistance of 1 meter of copper wire with a cross-sectional area of $1 \mathrm{~mm}^{2}$ is $\frac{1}{55} \mathrm{ohm}$.