The voltages demonstrated in the circuit of figure in below have no assigned directions demonstrated but have the magnitudes as given here:
V1 = 3V, V2 = 4.5V, V3 = 7V, V4 = 2.5V and E1 = 6V, E2 = 20V, E3 = 2E4.
By applying Kirchhoff's Voltage Law to the circuit, find out the polarity and value of the voltages E3 and E4.