Find the current flowing through the resistance `R_(1)` of the circuit shown in Fig. If the resistances are equal to `R_(1) = 10 Omega. R_(2) = 20 Omega` and `R_(3) = 30 Omega`, and the potential of points 1,2 and 3 are equal to `varphi_(1) = 10 V, varphi_(2) = 6V`, and `varphi_(3) = 5 V`
A. 15 V
B. 20 V
C. 25 V
D. 8 V
