In the circuit shown the cells \( A \) and \( B \) have negligible resistances. For \( V_{A}=12 ...

In the circuit shown the cells \( A \) and \( B \) have negligible resistances. For \( V_{A}=12 \mathrm{~V}, R_{1}=500 \Omega \) and \( R=100 \Omega \) the galvanometer \( (G) \) shows no deflection. The value of \( V_{B} \) is
(a) \( 4 \mathrm{~V} \)
(b) \( 2 \mathrm{~V} \)
(c) \( 12 \mathrm{~V} \)
(d) \( 6 \mathrm{~V} \)