+-2.5 points OSUniPhys1 27.3.WA.030.Tutorial.
Find the potential difference between point a and point b for the situation shown below. Here $\mathcal{E}_1 = 12.0 \text{ V}$, $\mathcal{E}_2 = 8.27 \text{ V}$ and $R_1 = 4.13 \Omega$, $R_2 = 6.04 \Omega$,
and $R_3 = 1.88 \Omega$.
$V_a - V_b = \text{____} \text{ V}$