$E_1$ and $E_2$ are two batteries having emfs of $3 \mathrm{V}$ and $4 \mathrm{V}$ and internal resistances of $2\mathrm{\Omega }$ and $1 \Omega$ respectively. They are connected as shown in figure below. Using Kirchhoff's laws of electrical circuits, calculate the currents $I_1$ and $I_2$.