In the following circuit, a $10 \, m$ long potentiometer wire with resistance $1.2 \, \Omega/m$, a resistance $R_1$, and an accumulator of $emf$ $2 \, V$ are connected in series. When the $emf$ of the thermocouple is $2.4 \, mV$, the deflection in the galvanometer is zero at a balancing length of $5 \, m$. The current supplied by the accumulator is:

• A
  $4 \times 10^{-4} \, A$
• B
  $8 \times 10^{-4} \, A$
• C
  $4 \times 10^{-3} \, A$
• D
  $8 \times 10^{-3} \, A$