$* *$ (a) Write Kirchhoffs rules for two loops and one junction in the circuit shown in Figure $P 16.39 .$ (b) Solve the equations for the current in each branch of the circuit when $\varepsilon_{1}=10 \mathrm{V}, \varepsilon_{2}=2 \mathrm{V}, R_{1}=50 \Omega$ $R_{2}=200 \Omega,$ and $R_{3}=20 \Omega$ (c) Determine the potential difference across resistor $R_{3}$ from point $\mathrm{B}$ to point $\mathrm{A}$